LEYSOP 5000 Series User manual

5000 SERIES
High Voltage Differential Amplifier
Serial No
LEYSOP 18 Repton Court, Repton Close, Burntmills, Basildon, Essex, SS13 1LN
ENGLAND.
Telephone: 01268 - 522111 Fax: 01268 - 522111
e.mail: [e-mail]

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THIS MUST BE READ BEFORE USING THE
5000 SERIES AMPLIFIER
5000 SERIES AMPLIFIER
WARNING
THE MAXIMUM OUTPUT UNDER NORMAL CONDITIONS FROM EITHER A OR B
OUTPUT CHANNELS IS 3.2kV. UNDER FAULT CONDITIONS MAXIMUM OUTPUT
VOLTAGE COULD RISE TO 4.5kV. THESE OUTPUTS ARE POTENTIALLY
LETHAL AND EXTREME CARE MUST BE USED IN BOTH USE AND SERVICING
OF THE AMPLIFIER. IT IS ESSENTIAL THAT THE OPERATING INSTRUCTIONS
BE EXPLICITLY FOLLOWED IN USE, AND SHOULD THERE BE ANY DOUBT ON
THE PART OF THE OPERATOR ABOUT THE USE OF THE AMPLIFIER THE
MANUFACTURERS SHOULD BE CONSULTED. THE OUTPUTS ARE FUSED AT
50mA.
The amplifier must not be operated out of its case. Only qualified
engineers in high voltage engineering should operate or service this
equipment
IMPORTANT
The amplifier is shipped with the four output valves removed and packed separately. These valves are
located inside the case. When they have been plugged in position, refit the amplifier into the case before
switching on.
The amplifier uses SHV output plugs. REMEMBER THAT THEY ARE LIVE AND POTENTIALLY
LETHAL.
IF FOR ANY REASON there is a short on the high voltage leads, the 50mA fuses located inside the
amplifier case, in front of the mains transformer will blow.

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5000 SERIES AMPLIFIER
SPECIFICATIONS
INPUT
Input voltage swing for linear operation + 2.5 V
Maximum permissible input voltage + 50 V
OUTPUT VOLTAGES
Normal voltage range for each channel 0.2 kV to 3.0 kV
Output voltage for zero input signal
and zero differential bias setting 1.7 kV each channel
Output voltages for zero input signal one channel 1.95
and maximum differential bias setting other channel 1.45
Output swing for + 2.5 volt input swing + 1.25 kV each Channel
about bias value
Effective differential output swing
for + 2.5 volt input swing 5 kV
Gain (differential output swing) 1000 ( + 2% )
(input swing)
INTERNAL OSCILLATOR
Frequency range 1 Kz - 10 kHz in 4 ranges
Amplitude Continuously adjustable
up to approx. + 2.5 V pk-pk
Functions Sine, square, triangular
OUTPUT CURRENT
The amplifier is not designed to provide output current into resistive loads.
The output is fused at 50mA.

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NOTE
The amplifier has been designed to have a small signal frequency response from dc. to 100 kHz.
At large signals the frequency response is limited by (1) the slew rate and (2) the allowable
power dissipation. At full amplitude the amplifier has a bandwidth limited to 20kHz due to
power dissipation.
DO NOT OPERATE AT FULL AMPLITUDE ABOVE 20KHZ
FREQUENCY RESPONSE
Maximum amplitude (5kV differential) frequency
response before significant distortion dc to 20 kHz
Time limitation for maximum output voltage
swing at frequencies above 10 kHz 30 seconds
RISE TIME 5 - 6 uS
SLEW RATE LIMIT 800 v/uS
PREAMPLIFIER FUNCTIONS
Positive limit Variable over 0-100%
of positive differential
output swing VA- VB
Negative limit Variable over 0-100%
of negative diff. output
swing VB- VA
Input bias/differential bias Varies differential
output over range + 0.5kV
Slew rate limit
off 800 V/uS (basic H.V.
amplifier slew rate
1 500 V/uS ) approx.
)
2 50 V/uS ) values
)
3 5 V/uS ) only
MAINS INPUT 250, 220, 200 volts,
50 Hz

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5000 SERIES AMPLIFIER
OPERATING INSTRUCTIONS
MAINS VOLTAGE SELECTOR AND FUSE
Before switching on the amplifier check the mains voltage selector, situated at the rear of the cabinet, is
set correctly and note that the mains fuse 2 Amp, 20mm type is mounted in the voltage selector. Fit the
output values by removing the amplifier from its case. Make certain that the amplifier is screwed back
into its case before switching on.
SWITCHING ON
Switch on the mains switch and note that the mains lamp comes on.
An internal delay circuit prevents the E.H.T. from switching on for a period of about 30 seconds. After
this time, the E.H.T. indicator will come on if the E.H.T. switch is in the ON position. The amplifier is
now ready for use, although it is recommended that full output swing at frequencies above 10 kHz should
not be demanded for a period of 5 minutes after switch on from cold.
NORMAL OPERATION
For normal operation the controls should be set as follows:-
DIFFERENTIAL zero
POSITIVE LIMIT 100%
NEGATIVE LIMIT 100%
SLEW RATE LIMIT off
The input to the amplifier may either be via the EXT input (linear range + 2.5 volts) or any of the wave
forms, square, sine or triangular from the internal oscillator as selected by the 'source selection' switch.
The frequency of the internal oscillator may be varied over the range 1Hz to 10 kHz. In addition, the
amplitude of the internal oscillator signal may varied over the range zero up to + 2.5 volts (100% setting)
by the amplitude control. The auxiliary outputs provide sine, square and triangular wave forms of
approximately constant amplitudes of + 2.5V pk-pk, irrespective of the wave form selected by the 'Source
selector' switch and also independent of the amplitude control.
DIFFERENTIAL BIAS CONTROLS (INPUT BIAS CONTROL)
The 'Differential bias controls' adjust the mean levels of the A and B output channels.
With the bias control set to zero both A and B channel outputs will be biased to 1.7 kV. When the
'Differential bias' controls are set to positive maximum (10%) the A output bias will be 1.95 kV, and the
B output bias will be 1.45 kV. Thus VA- VB= 0.5 kV which is 10% of the maximum differential output.
When the 'differential bias' controls are set to negative maximum, A output bias is 1.45 kV and B output
bias is 1.95 kV. The Differential bias control/input bias control allows the output levels to be precisely
adjusted across the pockels cells for 'zero voltage input conditions', thereby achieving the best extinction
ratio or lowest residual phase modulation.

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OPERATION OF LIMITS
The maximum positive differential output voltage VA- VB,may be precisely limited by the 'positive
limit' control. This is calibrated 0-100% which corresponds to a VA- VBlimit of between 0 and 2.5 kV.
Similarly the 'negative limit' control precisely limits the voltage VB- VAover the range 0 to 2.5 kV. As
an example, suppose it is required to limit the differential output swing (VA- VB)to between + 0.75 kV
and -1.25 kv, the proper settings for the limit controls will be as follows:
'Positive limit' control (0.75 x 100)% i.e. 25%
(2.5)
'Negative limit' control (1.25 x 100)% i.e 50%
(2.5)
Note that the differential bias control acts 'after the limiting process.
The main use of the limit controls is to provide two precise differential output voltages when the input of
the amplifier is driven from a square wave. This will allow fast switching between two stable precisely
set polarisation states in a pockled cell, or between two levels of optical transmission when the pockled
cell is used between crossed polarisers. The 'Differential bias' control allows adjustment of the residual
birefringement of the pockel cell, without affecting the limiting polarisation state.
The diagrams of Figs. 1(a), 1(b), 1(c) further illustrate the operation of the limit controls.
Fig 1(a) Shows the A and B output voltage VA and VB and also the differential output voltage (VA-
VB) when both limit controls are set to 100%.
Fig 1(b) Shows VA, VB and (VA - VB) when the limit controls are set to
'POS LIMIT' = 50%
'NEG LIMIT' = 100%
Fig 1(c) Shows VA, VB and (VA-VB) when the limit controls are set to
'POS LIMIT' = 100%
'NEG LIMIT' = 50%
It can be seen in Fig 1(b) that the setting the 'POS LIMIT' control to 50% limits the positive excursion of
VA to 2.275 kV while at the same time limiting the negative excursion of VB to 1.025 kV. The
corresponding value of the differential output voltage (VA - VB) is + 1.25 kV which is 50% of the
maximum possible positive output voltage.
Similarly in fig. 1(c) the setting of the 'NEG LIMIT' control to 50% limits the negative excursion of VA to
1.025 kV and the positive excursion of VB to 2.275 kV. The maximum negative differential output
voltage (VA - VB) under these circumstances is 1.25 kV which is 50% of the maximum possible negative
differential output voltage.

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SLEW RATE CONTROL
This limits the maximum rate of charge of differential output voltage. The main use of this control will
be to limit the rate of charge of voltage across a pockel cell when the input is a square wave of fast rise
time. If the amplifier is to be used for switching an EM500 modulator the maximum slew rate of
800V/uS may cause mechanical resonance, through piezo-electric effects, and unwanted optical
modulation through the elasto-optic effect.
0.4Kv
1.65Kv
2.9Kv VA
VB VB
VA
VA
VB
2.5Kv
1.25Kv
0
1.25Kv
2.5Kv
VA-VB
VA-VB
VA-VB
(c)(b)(a)
Fig. 1. Showing the effect of limit controls.

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ASIMPLE SETTING UP AND FAMILIARISATION PROCEDURE FOR THE
5000 SERIES AMPLIFIER AND EM500 SERIES MODULATION
BEFORE SWITCHING ON
First check that the amplifier input voltage selector is correctly set and that the amplifier output valves
have been plugged in.
THEN
1. Connect the modulator to the amplifier using the two leads provided.
2. Set internal oscillator to 1Hz with amplitude at min.
3. Set Input Slew rate switch OFF and Source switch to square wave.
4. Set positive and negative Output Limits fully clockwise.
5. Check that the amplifier is working by observing the monitor output using the oscilloscope.
6. Hold the modulator between two squares of polaroid with the axis of the polaroid film lying
along the radial axis of the BNC HV sockets and observe a white light source through this
combination. With the polaroids crossed a MALTESE fringe pattern should be seen thus.
As the 1Hz square wave output is increased the Maltese Cross will be changed until at full
amplitude the cross will switch between right hand and left hand output polarisation states as
shown below.
Full +
Output & Sense
Voltage -
There is then a phase shift between the ordinary and extraordinary rays leaving the modulator of
+ 180°.Precise square wave + phase shifting can be achieved between 0 - 180°by adjustment of
the limit potentiometers.
7. If one limit potentiometer is set at zero, only one side of the modulator crystal is driven and the
output polarisation state will switch in one direction only. This arrangement can be used for
amplitude modulation of a laser beam.

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SETTING UP THE MODULATOR WITH A LASER BEAM
The input polarisation must be along the BNC axis or at 90°to that axis.
Asuitable output polariser should be crossed to the input polarisation state.
Initially set up the modulator with back reflections along the beam axis. Place a fine ground glass screen
between the input polariser and the modulator and a Maltese cross should be observed after the analiser.
Adjust the modulator position until this cross is central to the beam axis. The best extinction ratio is then
achieved. This must be performed with the EHT switched OFF.
PARTS LIST.
1off 5000 Series amplifier
2 off HV leads 1 M in length with connectors
1off Mains lead