Bradley 233 User manual

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INSTRUCTION MANUAL

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G. S. E. BRADLEY LTD.
Electral House, Neasden Lane, London, N,W.10
Telephone: 01 ^50 TBII Telex: 25583

AMENDMENT RECORD SHEET
Incorporation of an Amendment List in this publication is to be recorded by
signing in the appropriate column and inserting the date of making the amend
ments.
A. L. AMENDED BY DATE
Although every care has been taken to ensure that the information contained in
this manual is accurate at the time of going to press, continuous development
may result in equipment changes and consequent inaccuracies in the Manual.
The Company reserves the right to institute such changes as and when necessary
without prior notification.

Reproduction of this document, or any part of it, without written permission
from G. & E. Bradley Ltd., is prohibited.
GUARANTEE
We will make good by repair or replacement any defects in products of our
manufacture not caused by wear and tear, accident, mis-use or neglect,
provided.
(1) that such defects are brot^ht to our notice not later than 12 months
from the date the goods were first despatched and
(2) that no unauthorized repair or replacement has been previously carried
out or attempted. We do not guarantee the products of other
manufacturers which form part of the goods of our manufacture, but
will pass on to our customer the full benefits we have received in
repsect of guarantees offered by such other manufacturers in respect
of their goods.
This guarantee is given in lieu of any warranty implied by statute or otherwise,
and our liability thereunder is expressly limited to the cost of the repair or
replacement made by us or to our order.
G. and E. Bradley Limited,
Electral House,
Neasden Lane,
London, N. W. 10.

CONTENTS
SECTION 1
1.1
INTRODUCTION
Performance
Page
1
SECTION 2
SPECIFICATION
SECTION 3 OPERATING INSTRUCTIONS
3.1 Installation
3. 2 Push Buttons
3. 3 Rotary Switches
3.4 Functional Description
3.5 'A' Functions
3. 6 'B' Functions
3. 7 Output Functions
SECTION 4 TECHNICAL DESCRIPTION
4.1 Timing Section
4. 2 Output Section
4.3 Power Supplies
SECTION 5 SERVICING AND ADJUSTMENTS
5.1 General
5.2 Mechanical Details
5. 3 Test Equipment
5.4 Power Supplies
5. 5 DC Voltage Test
5. 6 Input and Delay Functions
5.7 Timing
5. 8 Pulse Shape
5. 9 Offset Zero Check
13
13
18
19
21
21
21
21
21
22
23
24
25
26
SECTION 6
PARTS LIST
27
(ill)

LIST OF ILLUSTRATIONS
FRONTISPIECE
FIG. A and B
FIG. 1
FIG. 2
FIG. 3
FIG. 4
FIG. 5
FIG. 6
FIG. 6 (a)
FIG. 6 (b)
FIG. 6 (c)
FIG. 7
FIG. 8
FIG. 9
FIG. 10
Showing Advantage of Source Termination
Showing ECL Logic Circuit
Showing Logic Levels of ECL Gate
Multi-Vibrator Waveforms
Monostable Waveforms
Differentiator Waveforms
Timing Circuit
Period Switch Arrangement
Delay A + B, Width A + B. Switch Arrangement
Delay/Period. Switch Arrangement
Output Circuit
Power Supplies
System Output Circuit
Printed Circuit Board
(iv)

SECTION 1
INTRODUCTION
1.1 PERFORMANCE
The Bradley 233 twin channel pulse generator provides 0. 5Hz to 50MHz at up to 10 volts
positive or negative into 50fi.
Resistive or reactive loads of any magnitude may be driven. The 50n source impedance
('back match') at the generator will always produce a true 50fi source at the end of the cable.
The internal 50J2 can be switched out to provide full 10 volts into a 5052 external load.
Output Baseline offset provides any pulse amplitude from 0. 5 volts to 10 volts within the
limits ±10 volts. The parallel/serial delay allows pulse positions to be adjusted independ
ently or in groups.
The internal sum facility allows the two outputs to be summed without reduction in amplitude
or refelction in the interconnecting cables. This facility provides stepped or super-imposed
pulses up to 20 volts maximum amplitude.
Other features of the 233 are the internal burst facility by using the B delay generator as an
oscillator to be gated by the A width. The adjustable level control and slope selection per
mits triggering off any point on the input waveform. This operates down to zero frequency
whether on external trigger, gate or external width. A Trigger Indicator lights when the
input is correctly triggered.
Simplicity of operation is provided by the square-wave facility which eliminates the need to
adjust the delay and width controls.
The B period oscillator can be free-run independently of the A section thus providing
virtually two pulse generators in one instrument.
1 -

2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
2.12
2.13
2.14
2.15
2.16
2.17
2.18
Repetition Rate
External Input
Manual
Trigger Light
Pre-pulse Output
Delay and Width
Configurations
Internal Burst
Pulse Delay
Pulse Width
Timing Jitter
Timing Drift
Output Configurations
Output Amplitude
Polarity
Baseline Offset
Rise and Fall Times
Waveform Aberration
Output Protection
SECTION 2
SPECIFICATION
0. 5Hz to 50MHz (8 ranges).
DC coupled. Sensitivity 0.4V peak to peak. Minimum pulse width
5ns. Slope selection. Level variation ±4V. Maximum signal 50V
peak. Trigger, gate and external width modes available.
Single cycle, burst and d. c. level or slope modes available from
front panel push button.
Indicates correct level setting when an external input is supplied,
whether used for triggering or gating. Single flash when manual
button is depressed.
Minimum +2V pulse from 50 ohm source. Risetime less than 5ns.
Occurs less than 20ns after triggering from an external source.
Width about 250ns at low frequency reducing automatically to
approximately 10ns at 50MHz.
Two delay plus width chains. May be driven in parallel from the
internal or external period signal, or in series, in which case the
B delay triggers off the trailing edge of the A width.
B delay converts to a period oscillator, gated by width A.
20ns to Is. (Pre-pulse to Main pulse).
10ns to Is. Maximum duty cycle 50% at minimum vernier
increasing to 80% at maximum vernier.
Less than 0.1%. / V ' "f ^ 6 ' ^ ^
Approximately 0.1%/°C.
Two independent output channels. Each can be driven from A and/
or B pulse width or period signal. Each has polarity and comple
ment selection, independent amplitude and offset controls.
Continuously variable 0. 5V to lOV into 500. Internal summation
controlled by push button. Outputs add algebraically into output 2
and output 1 becomes non-operative.
Positive or negative.
0 to -lOV (Positive pulse).
0 to +10V (Negative pulse)
5ns typical.
Less than ±5% at amplitude greater than 2V (with 500 termination).
Short circuit and overload protected.
- 3 -

2.19
2. 20
2. 21
Power Supplies
Temperature Ranges
Dimensions
100-125V or 200-250V. 50/60Hz. Approximately 35VA. All
supplies regulated.
Operation 0 to 50°C
Storage -10 to+60°C.
2.22
Weight
For Rack Mounting
Height: 90mm (3.1/2")
Width: 310mm (12.1/4")
Depth: 280mm (11")
5.5kg (121b).
Overall - includes feet Handles and
Controls.
115mm (4.1/2")
332mm (13.1/8")
322mm (12. 3/4")
- 4

SECTION 3
OPERATING INSTRUCTIONS
3.1 INSTALLATION
1. Check that the rear panel voltage selector switch is set correctly for the supply voltage.
2. Fuse ratings: for 200/250V operation - 0. 5A (supplied)
for 100/125V operation - lA.
3. Supply connections
Brown - Line
Blue - Neutral
Green/yellow - Earth
3.2 PUSHBUTTONS
1. The legend above any push-button refers to the function obtained when the button is in.
2. Black buttons occur in interactive groups, and normally only one button should be in.
3. White buttons are mechanically independent, and the legend below a button refers to
the function obtained when the button is out. It is screened in yellow as a reminder.
4. The red button has a spring-return action.
3.3 ROTARY SWITCHES
1. On all time switches the nomimal value of the switch setting is obtained when the small
concentric vernier control is fully anti-clockwise in the 'CAL' position. When the
vernier is turned clockwise the time increases until it overlaps the next greater range
setting; or on the longest range, overlaps a value ten times greater than the range
setting.
2. Stable pulses can be guaranteed only when the delay and width monostables are not
"counting down". It is important, therefore, to keep both delay and width of a pulse
somewhat less than the period. If the delay is not required, set it to lOnsec.
3. Jitter, or at high frequencies, moding can be caused by any delay or width monostables
counting down. It is good practice to keep all unused delay or width contols set to
lOnsec.
4. On the output amplitude controls the nominal value of the switch setting is obtained
with the vernier fully clockwise in the 'CAL' position. The vernier reduces the
amplitude until it overlaps the next smaller range setting, or on the lowest range,
until it is less than 0. 5V.
3.4 FUNCTIONAL DESCRIPTION
1. A Section
This section determines the pulse rate for the rest of the unit. On "Free Run" and
"Ext Gate" the rate depends on the settings of the PERIOD switch and vernier. On

"Ext Trig" it depends on the frequency of the external signal applied to the input socket,
and on "Single Cycle" on the rate of pressing the Manual (Red) button).
The duty cycle of the rate signal is of interest because the output sections can be
driven directly by this rate signal by selecting "squarewave" at the output. On "Free
Run" the duty cycle is approximately 50%, i.e. a squarwave. On "Ext Trig" it is the
same as the external signal, if this is a pulse of fast rise time, but this will depend on
the setting of the "Level" control particularly if the edges are slow. Selecting negative
"Slope" converts the signal to its logical complement. On "Single Cycle" the signal is
a pulse of width equal to the time that the manual button is held in.
The pre-pulse and the A delay are both initiated by the positive edge of the rate signal.
2. B Section
On "Parallel Delay" the B delay is also initiated by the positive edge of the rate signal.
On "Serial Delay" the B delay starts at the end of the A width.
When "Gated By Width A" is selected, the B delay becomes an oscillator gated on
synchronously by the A width.
By pressing both the "Parallel Delay" and "Gated By Width A" buttons, control of the
"B" oscillator is released by the 'A' section thus allowing the 'B' oscillator to free
run.
3. Output Sections - See Fig. 7
The A and B widths drive the output sections via a logical OR function. When neither
is selected the rate signal drives the output (see 3.4.1). The "Comp" function, when
selected, inverts the signal before it reaches the output amplifier.
The output stage is a current source (high impedance) with a shunt 50fi resistance,
(which can be switched out with the cover removed, see 3.7.7). This type of output
can drive resistive and reactive loads of any magnitude without limiting. The output
impedance at the end of any length of 50i2 cable is therefore always 50J2 and resistive,
whatever the terminating impedance. This is because all reflections are absorbed at
the generator.
On "Sum" the two output current sources are switched into output 2, shunted by only
one 50fi resistor.
3.5 'A'FUNCTIONS
3. 5.1 Free Run
This function selects the internal oscillator, (whose rate is controlled-by the "PERIOD"
switch and vernier) as the main signal source for the instrument.
3. 5. 2 Square-wave
Select "Free Run", and "Square-wave" on the output in use. All delay and width controls
are then ineffective on that output. Nevertheless, at high frequencies it is advisable to set
them all to minimum, to prevent the chance of visible sub-harmonics on the output signal.

3. 5. 3 External Trigger
Select "Ext Trig", and A and/or B on the output in use. Each time the selected slope of the
input waveform crosses the threshold level a pulse cycle will be initiated.
3.5.4 External Width
Select "Ext Trig", and "Square-wave" on the output. When positive slope and a normal
positive output are selected, the output will be high when the input signal is above the thres
hold level. When the input signal is a pulse the output will have essentially the same width.
3. 5. 5 External Gate
In this mode the "PERIOD" oscillator is the signal source of the instrument but it is able to
oscillate only whilst the sutput signal is above the threshold level (with positive slope selected).
The "PERIOD" signal starts synchronously with the input signal, but delayed by a fraction of
a cycle. ^ _
3. 5. 6 Countdown Sync.
On "External Gate" and when the input frequency is higher than the PERIOD frequency. The
'PERIOD' oscillator can be synchronised by the input signal up to a frequency ratio of
100 : 1.
3.5.7 Slope
This is used to select which slope of the input waveform triggers the unit (initiating pre-
pulse; delay A and on parallel delay, delay B), or which part of the waveform is used for
the external width, or gating signal. On positive slope, this is the part above the threshold
level.
3.5.8 Level Control
Can be used to vary the level on the input waveform at which triggering will occur. It can
also be used to vary the threshold level to allow triggering from signals which are offset,
from earth potential.
3. 5. 9 Triggered Light
Each time the input signal crosses the threshold level the lamp flashes. At frequencies
above a few cycles per second the lamp appears to be on continuously. It is useful in setting
the trigger level, and at low rates to give a clear indication of the instant of triggering.
3. 5.10 Single Cycle
Select "Single Cycle", and A and /or B on the output in use. Press the red button to start a
cycle.
3. 5.11 Manual Step or Level
Select "Single Cycle" and "Square-wave" on the output. Pressing the red button produces a
fast step, and a d. c. level whilst the button is held in.
3. 5.12 Manual Burst
Select this function by part-pressing one of the four black buttons which is out, so that they
- 7

are all out. The red button can then be used to gate the "PERIOD" oscillator, in a manner
similar to a morse buzzer.
3.5.13 Pre-pulse
The pre-pulse is useful for triggering oscilloscopes, circuits under test or other pulse
generators at "zero time" with respect to the delayed output pulse. It is a positive going
pulse of greater than 2V into an open circuit or IV into 5012. It is not necessary to terminate
the cable, provided that it has a characteristic impedance of 50S2. At low frequencies the
pulse width is about 250nsec so that it is easily visible on an oscilloscope, and has enough
energy to trigger medium speed devices. At higher frequencies the pulse width reduces to
lOnsec at 50MHZ.
3.6 'B'FUNCTIONS
3. 6.1 Parallel Delay
On parallel delay the A and B delays start simultaneously, on the trigger from the PERIOD,
input signal or from the action of the manual button. This allows one pulse to be delayed
"through" the other.
3.6.2 Serial Delay
In this mode the B delay is initiated by the trailing edge of the A width, allowing a pulse pair
to be moved as a group, using the A delay control.
3.6.3 Internal Burst
Selecting "Gated By Width A" converts the B delay circuit to an oscillator, synchronously
gated by the A width. Select only B width on the output unit. Keep the B width setting roughly
the same as the B period setting. Ensure that it is not dividing the frequency by being set too
wide. Set the A width to at least ten times the B period. Then make fine adjustments as
necessary.
3.6.4 Two Frequency Sources
Press "Parallel Delay" and "Gated By Width A" simultaneously so that they both remain in.
The B period oscillator will then free-run. There is a slight tendency for the oscillators to
phase lock to the same frequency or to a low order sub-harmonic, particularly at high fre
quencies, but for most purposes this effect will be negligible, and probably not noticeable.
3.7 OUTPUT FUNCTIONS
3.7.1 Signal Source Selection
The A and B buttons on each output section determine whether the output pulse is width A,
width B or both. When both A and B are selected on one output, there will be no increase in
amplitude where the pulses, overlap. The two pulses are combined by a logical OR function
before the output amplifier, whose two output level states are set by the offset and amplitude
controls.
A square wave will be obtained when both A and B buttons are out and "Free Run" is selected.
In the "Ext Gate" mode this will become an interrupted square wave - if an external input
signal is present and the level control is correctly set. On "Ext Trig" or "Single Cycle" the
output state will depend on the input state, or manual button position.

3.7.2 Normal/Complement
The complement function logically inverts the input signal to the output amplifier. The levels
of the two output states are unchanged, but where the output was in one state, it goes to the
other.
This function is useful when pulses of duty cycles approaching 100% are required or, in
combination with the polarity switch to obtain a greater range of pulse baseline offset, (see
3.7.3).
3.7.3 Amplitude and Offset Polarity
When the offset is set to zero and a positive pulse is selected, the output is a pulse of
positive amplitude with a baseline at earth potential. Clockwise rotation of the offset
control will lower the baseline to -lOV.
If a pulse of high duty cycle is required, select "Comp".
If positive offset is required without change of duty cycle, reverse the state of both "Norm/
Comp" and "+/- pulse" buttons. With negative pulse selected the baseline of the pulse
becomes the more positive level. This upper level of the pulse can now be varied between
0 and +10V.
3.7.4 Summed Outputs
When the "Sum" button of Output 1 is pressed, the amplitude and offset of Output 1 amplifier
is added into Output 2. To prevent distortion the controls must be set so that no part of the
combined waveform lies outside the range -lOV to +10V. Output 2 toggle switch must be in
the internally terminated position. It is preferable to terminate Output 1 to prevent
deterioration of the Output -3TTkiiftlt.tiJFs.
To obtain an amplitude greater than lOV, select the same signal source and output polarity
on each output using one offset control to keep the output in the -lOV to +10V rai^e.
3.7.5 Termination ; Discussion
(a) End Termination
It is a common convention to quote pulse generator amplitudes into 50S2. This
pre-supposes that a 50fi terminating load to earth is always used at the far end of the
co-axial cable from the pulse generator, thus matching the cable (which should be 50fi
characteristic impedance) and preventing reflections.
Output pulses photographed under these ideal conditions enhance the advertising
literature.
In normal use, however, the load to be driven is rarely a true 50fi resistance, and is
often reactive and non-linear. When such a load is connected across the 50S2
termination, reflections occur, and if the generator is not carefully matched to the
cable repeated reflections at each end of the cable cause ringing of slowly dying
amplitude at the load. At high pulse repetition frequencies these rings combine with
the next transmitted pulse, addding to or subtracting from the leading edge, depending
on phase.
Many pulse generators are, however, dependent on a 50fi load for their correct
functioning. It is usually only when they are attenuated to half amplitude or less by the
front panel controls producing a fairly good match at the generator that the problem of
multiple reflections is overcome.
- 9 -

(b)
Source Termination
One end of a cable must be matched to prevent multiple reflections.
Most pulse generators are designed to use only one termination at full amplitude,
otherwise the voltage or current requirements are double.
Because the load to be driven by a general purpose pulse generator should preferably
be unspecified, the more satisfactory solution is to match the source.
With source termination the amplitude of the wavefront launched into the cable is half
the open circuit output voltage. This is because the cable itself presents a SOP load to
the pulse generator until the wavefront is reflected. If the end of the cable is open-
circuit 100% reflection occurs, but the reflected wavefront is absorbed in the source
termination. The waveform at the end of the cable is a single step at the full open cir
cuit amplitude.
The overall effect is that at the end of the cable the pulse generator presents a clean
pulse from a SOP source impedance.
A clear demonstration of the superiority of source termination is provided by exam
ination of the case of a load consisting of a 4.7/nF capacitor with one inch leads. With
end termination, rings of S% full amplitude are still present after 2S0nsec(4ft cable
length). This ringing is superimposed on the CR response. Fig. A.
Using source termination the waveform is a single 2V Snsec spike followed by a clean
CR response. The spike is caused by the lead inductance (of about 50nH) differentiat
ing the output pulse. There is no visible reflection and the cable length does not affect
the waveform. Fig. B.
Fig. A.
Fig. B.
Deflection Factor 2V 50ns
- 10 -

3. 7. 6. 233 Termination and Load Capability
Because of the arguments of 3. 6. 5. the 233 has been designed especially for source
termination, and care has been taken to minimize reflections at the generator.
Loads of any magnitude, whether resistive, inductive or capacitive may be driven without
limitation.
A series tuned circuit can cause the output voltage of the pulse generator to over-swing by
up to 70% of amplitude in special circumstances. In these cases the output voltage must be
kept within ±10V using the amplitude or offset controls.
For loads returned to voltages other than earth potential, or for active loads, the only
limitation is again the need to keep the output voltage in the ±10V range. Within this range
the generator always acts as a true 50S2 source at the end of the 50fi cable.
3.7.7 lOV into 50R
When it is required to drive an external 50S2 load at more than 5V amplitude, the internal
5012 resistors may be switched out using printed circuit mounted toggle switches. To gain
access remove the screws at each side of the top cover and lift off the cover. Set the
switch levers towards the front panel to disconnect the internal loads.
3.7.8 20V from each Output, into lOOfi
By disconnecting the internal loads as in 3.7. 7 and using a 100S2 1 watt resistor at the end of
each output cable, up to 20V amplitude is obtainable. The offset control must be used to
keep the signal within the ±10V from earth.
With a 4ft. 5012 cable the risetime will deteriorate. There will be a fast step of 2/3
amplitude, followed after 20 nanoseconds by another step 2/3 of the remaining amplitude
and so on. Better edges will be obtained with 7512, or preferably 100J2 cables.
- 11 -

SECTION 4
TECHNICAL DESCRIPTION
4.1 TIMING SECTION (Printed Circuit Prefix 100. Fig.6)
The functions of the integrated circuits are as follows:
ICIO Input amplifier, Schmitt trigger and Period multivibrator.
IC20 Delay A.
IC30 Width A.
IC40 Delay/Period B
IC50 Width B
IC60 Trigger-light circuit
IC70 Pre-pulse circuit
All the integrated circuits are E. C. L. (emitter-coupled logic) (fig. 1) and the logic levels
(fig. 2) are approximately:
Logic High or 1 -0. 9V
Logic Low or 0 -1. 9V.
These voltage levels do, however, depend on the supply voltage.
The output emitters are open circuit, and therefore normally require a 'pulldown' resistor
to the negative supply of the package.
Inputs have internal 'pulldown' resistors to hold the transistors off when the inputs are not
used.
(For more information on this logic family, read the general section of the Motorola 10, 000
series handbook).
The applications of the E. C. L. gates are:
1. Amplifier
2. Schmitt Trigger
3. Inverter.
4. Non-inverting Buffer.
5. Multivibrator.
6. Mono stable.
7. Differentiator.
8. Catching Diode.
9. Lamp Driver.
10. Transistor Driver.
and the occurrences of these are shown in the table below.
IC
a
b c
d
10 1
2
5
3
20
3,7
7 6
8
30
77
6
8
40
7
7 6
8
50
7 7
6
8
60
4
8 6, 9
-
70
4
8
10 10
13

4.1.1 Amplifier
Fig. 2 shows that a gate has gain when its input is near to -1.3V,but when the outputs reach
the logic levels they are limited and the gain is zero.
vcc (ov)
OUT O-
IN 1 O-
IN 2 O-
1_.
VBB
-O OUT
J
VEC (-6V)
FIG.1 E.C.L. LOGIC
IN 1
IN2
&
OUT
• OUT
THRESHOLD
-1-3
V IN
OUT
OUT J
-0-9V HIGH STATE
-1-3V
-1 ■ 9V LOW STATE
V OUT
fig. 2 LOGIC LEVELS
- 14

4.1. 2 Schmitt Trigger
The action of IClOb is as follows:
As the input to R16 goes high, with pin 6 low, pin 7 reaches the logic threshold. Positive
feedback from pin 6 to pin 7 then causes pin 6 to snap into the high state.
Note that the output at pin 6 is in phase with the input to R16.
4.1.3 Inverter
IClOd inverts the Schmitt output so that it is in phase with the starting edge of the PERIOD
multivibrator lOd in the gated mode.
The triggering edge from ICIO is negative going, as required by the differentiators at the
input to the delay circuits.
IC20a inverts the signal so that the external width signal and the internal square-wave are in
phase with the A and B widths at the input of the output circuits.
4.1.4 Non-inverting Buffer
IC60a and 70a prevent capacitive loading on signals used for other purposes.
4.1. 5 Multivibrator (Waveforms : Fig. 3)
Pins 3 and 15 of ICIO perform a 'wired OR' function, a high state overpowering a low state.
Thus when pin 6 is high, the output of pin 3 has no effect on the output at pin 15. IClOc then
becomes a free-running relaxation oscillator. The output at pin 15 is always anti phase to
that at pin 9 so that the current through Rll discharges Oil until the voltage at pin 13 reaches
the threshold. Positive feedback through Gil causes the signal at pin 9 to snap into the other
state, taking pin 13 one logic swing away from the threshold. It then proceeds to drift back
towards the threshold.
When the Schmitt output pin 3 forces pin 15 into the high state oscillations stop,with pin 13
and pin 9 also in the high state, without curtailing the negative half cycle at pin 9.
When the Schmitt allows pin 15 to return to the low state, pin 13 drifts down to the threshold.
There is a delay of about a quarter period before the first negative active edge at pin 9.
This delay does, however, ensure that the first period is equal to succeeding ones.
IC 10 PIN 6
.. PIN 13
— PIN 15
OUTPUT
PIN 9
FIG. 3 MULTIVIBRATOR WAVEFORMS
15

4.1. 6 Monostable (Waveforms : Fig. 4)
In the quiescent state pins 13, 12 and 9 of IC30 are in the low state. A trigger pulse at pin 13
drives pin 9 into the high state, which drives pin 12 through C31. The high state at pin 12
holds pin 9 through gate action. The trigger pulse is narrower than the minimum pulse width
of lC30c, but is wider than the gate propagation delay, to allow latching of pin 12.
The voltage at pin 12 then decays at a rate dependent on the current through R31 and the value
of C31, until it reaches the threshold. Then positive feedback through C31 causes pin 9 and
12 to snap down together until pin 12 is caught at the low level by the output emitter of pin 14.
Pin 9 continues the rest of the way to the low level at a rate dependent on the current in R32,
and the value of C31. This ramp determines the recovery time. If the monostable is triggered
during this recovery time, the output will be a narrower pulse than normal.
1C20, 40 and 60 work in a similar fashion, but 1C40 can be switched to an astable multi
vibrator mode.
The circuit of 1C60 differs in being triggered directly at the
INPUT TRIGGER
10 30 PIN 13
PIN 12
OUTPUT
PIN 9
I,
FIG.4 MONOSTABLE WAVEFORMS
- 16 -