Modulator driver amplifiers:
High voltage Pockels Cells driver amplifiers
Q-switch step high voltage pulse generators
250 Series High Voltage Video Amplifier
 This is a linear Class A output video amplifier with a maximum
differential output of 275V over the range d.c. to 7MHz. The two
outputs can also be set to ±250V dc
relative to each other using a bias control. This facility allows an
electro-optic amplitude modulator to be set to any desired light
output intensity level for any input signal level. This output bias
does not introduce any limit to the signal output range.
The amplifier has been designed to drive electro-optic modulators
from the EM200 range where the load is purely capacitive and does
not exceed 100pf. The output is short circuit proof.
Specifications
| Signal output voltage
range |
275Vdc - 6MHz bandwidth
|
Amplifier Square Wave
Rise & Fall Time
using 100pf load |
< 65 ns (10% - 90%)
|
| Bias Voltage Range
|
+250V to -250V
|
| Input Voltage for Full
Output |
±1Vdc or 2Vpp., ac
|
| Input Impedance
|
50
Ω
nominal |
| Cabinet Size (mm)
|
Height 220, Width 530,
Length 340 |
| Mains Voltage
|
110/200/240ac 50-60Hz
|
| Temperature Range
|
0° - 40°C ambient
|
5000
Series High Voltage Linear Differential Amplifier
 This 5000V series linear amplifier has been designed to
drive large aperture electro optic modulators. It consists
of two 0.4 - 3.0 kV linear amplifiers that together produce
a differential output that can be connected to either side
of the modulator. This produces an optical phase change
equivalent to the output from a single sided 5000V unit.
The amplifier has a bandwidth of 14KHz and a rise time of
less than 5µs.
It incorporates a 1 - 10KHz internal oscillator giving
sinusoidal, triangular and square waveforms. For phase
modulation applications the positive and negative excursions
of the square wave output can be precisely controlled. This
differential drive technique increases the lifetime of the
modulator by maintaining a zero mean voltage across its
terminals.
Specifications
| Output Voltage Range
|
400 - 3000V (each
side) |
| Full amplitude
Frequency Response |
14 KHz |
Small Signal
Frequency Response
(10% Full Amplitude) |
100KHz |
| Rise and Fall Time
|
5µsec |
| Signal-Noise Ratio
|
50dB |
| Input Voltage
|
-2.5V to + 2.5V
|
| Input Impedance
|
1000Ω
|
| Cabinet Size (mm)
|
220 (height), 530
(width), 340 (length) |
| Mains Voltage
|
110/200/240ac
50-60Hz |
HVP50/80 High Voltage Pockels Cell Q-Switch Driver
| Step Pulse Generator |
HVP 50/80 |
|
Output Pulse |
| Voltage Range |
1 - 8 kV |
| Maximum Output current |
200 A |
| Electrical Falltime |
< 3 ns |
| Recovery Time |
100 µs exponential |
| Output Impedance |
50
Ω |
Maximum on time at maximum
current |
200 ns |
| Maximum Repitition rate |
100Hz |
| Minimum Pulse Width |
10 ns |
|
External Trigger
Input |
| Amplitude |
-3 V to + 3 V |
| Polarity of Leading Edge |
Positive or Negative |
| Input Impedance |
50
Ω |
| Minimum Internal Delay |
40 ns |
|
Sync Output |
| Amplitude |
> 3 V into 50
ohms |
| Jitter wrt High Voltage Pulse |
100 ps |
|
Internal Rate
Generator |
| Repetition Rate |
0.1 Hz - 100 Hz |
Pulse Terminating
Load
(designed to correctly terminate a 50 ohm
coaxial cable) |
| AC Impedance |
50 ohms nominal |
|
Cabinet |
| Volume (W x D x H) |
330 x 330 x 100 mm |
| Weight |
4 kg |
|
Environmental
Temperature |
| Range |
0°C - 40°°C |
|
Supply |
| Mains Voltage @ 50 or 60 Hz |
120 or 240 V ± 10% |
| Power |
50W |
|
Enable Input |
| Removal of a short circuit will
prevent operation |
Applications
| Q-switching
|
Q-switching Opening Times
|
< 3 ns |
| Pulse Slicing
|
Optical Switching Time
|
< 3 ns |
Pulse Picking Using
4 - Terminal EO Modulator |
Cable length (50 ohm, 100 pF/m)
|
2 m - 4 m |
| Cable Delay
|
5 ns / m |
| Pulse Width
|
10 ns - 20 ns
|
| Optical Risetime
|
< 3 ns |
| Optical Falltime
|
< 3 ns |
Note: The HVP generator can be supplied giving a
output pulse of fixed length between 10 - 100 ns set.
100kHz RTP Pockels
Cell Q-switch Driver
One of the most difficult aspects in dealing with electro-optic
devices is the problem of working with high voltages. The majority
of electro-optic devices present a capacitive load to the driver
which further compounds the problem of finding a suitable driver.
However, the relatively low voltage requirements of the transverse
field RTP Pockels cell allow Leysop to switch the high voltage at high
repetition rates with acceptable power consumption at the driver.
Leysop developed the driver with the application of continuously
pumped sources in mind. For this reason no
facility for varying the delay from the input trigger pulse and the
Q-switch output pulse has been incorporated. Full protection
facilities are provided based on internal current limiting to ensure that the
demands on the internal HT power supply do not exceed its
capability. There is also an internal rate generator for those
applications where synchronization to external events is not
required and free running use is acceptable.
Safety is paramount and the high voltage output is
provided by a safe high voltage (SHV) form of the BNC connector and
a matching lead is supplied to connect to the Pockels cell
terminals. The HT votage may be set precisely from the front panel
to enable the unit to be set for optimum performance at the user's
operating wavelength and to allow for the different voltage
requirement of the three aperture options available.
Provisional Specifications:
| Parameter |
Value |
| Repetition Rate |
0 to 100kHz in five decade steps
by internal or external generator |
| Output Voltage |
+200 to +2,000V adjustable with
visual display |
| Output Pulse |
The standard system generates a
positive going step function above zero. The generator can
also be supplied giving a negative going step from the set
HT level down to zero for quarter wave switching |
| External Trigger In |
+3.0 to 10.0V min. 10ns f.w.h.m.
into 50Ω |
| Synchronization Output |
TTL approx. 30ns after trigger |
| Overload Protection |
(1) Repetition rates above
100kHz
(2) HT Current above 25mA
(3) Output stage fault overload
Protection occurs by automatic removal of the HT supply
which can be re-instated by the reset switch |
| Power Input |
Universal 90 - 265V a.c. 47 -
440Hz via fused IEC inlet |
| Dimensions |
150(h) x 250(w) x 330(d) (mm)
Mass: 6kg |
| Step Voltage at End of an Open
Circuit 50Ω Line |
| 50W co-axial
cable length |
Rise-Time |
Flat Top |
Fall Time |
Maximum Frequency at 2kV |
Maximum Voltage at 100kHz |
| 125mm |
5ns |
175ns |
400ns |
80kHz |
1,700V |
| 250mm |
5ns |
160ns |
500ns |
66kHz |
1,500V |
| 500mm |
<7ns |
150ns |
700ns |
50kHz |
1,300V |
| 1,000mm |
<8ns |
120ns |
1,000ns |
40kHz |
800V |
|
