PC25 Test Boardfor the A225/A206
The PC25 is a printed circuit board which accepts the A225 charge sensitive preamplifier and shaping
amplifier and the A206 voltage amplifier and discriminator. It is designed to be used for two purposes: tofacilitate testing of these devices, together or separately, and to simplify their use in many applications. The
board provides input test circuitry, gain adjustment, voltage reference for the A206, and convenient access toall active device pins. Ground plane construction minimizes noise pickup.

INPUTSINPUT:

A225, PIN 1; Charge preamplifier input.
This input is diode protected and must be
capacitively coupled to detector with capacitorof adequate rating. (Not supplied.)

DET:

Input from detector. See Operating Notes.

HV:Detector bias voltage.

TEST IN:

Input to test circuit as described inspecifications.

COMPONENTS
THRESHOLD
ADJUST (R3, R4): Potentiometer to provide trigger level
for the A206 discriminator.
C1, C2, C3, C5:

Filter capacitors.

CT:
RT:

Test capacitor (2 pF).
Test pulse termination resistor(50 ohm).

CW:

Discriminator pulse width adjustment
capacitor; A206, PINS 6 and 8.

RB:

Resistor to bias A206 for bipolar
inputs; 330 kohm from PIN 3 toground. (Not installed.)

DISC OUT: A206, PIN 9; Discriminator logic pulse out.

R5, R 6:

Gain control voltage divider.

10, 11:

CD:

Differentiating capacitor for bipolar
pulses. Direct connection for normal
unipolar pulses.

U 3:

Voltage reference device.

HV Res:

Detector bias resistor. (Not installed.)

HV Cap:Detector coupling capacitor (H.V.).
(Not installed.)

OUTPUTSTP OUT:

A225, PIN 12; Timing pulse.

OUTPUT: A225; PIN 8; Shaped output.
VA OUT:

A206; PIN 13; Voltage amplifier output.
A206, PINS 10 and 11, Monitor points.
Difference in potential between these pins is thediscriminator threshold level set by“THRESHOLD ADJUST” potentiometer.

POWER and GROUND
JP1:
A225, PIN 5; Output ground of A225. See
Operating Notes.
VS:

Power to the A225 and A206. See OperatingNotes.

SIZE

2.625 in x 1.750 in(6.67 cm x 4.45 cm)

Amptek Inc. 14 DeAngelo Drive, Bedford, MA 01730-2204 USA
Tel: +1 781 275-2242

Fax: +1 781 275-3470

Email: sales@amptek.com

http://www.amptek.com

PC25 Wiring Diagram for the A225/A206

PC25 Operating Notes
A2251)TESTING A225: The A225 may be tested simply by connecting power (+4 to +25 VDC) to “VS” and asquare wave to “TEST IN.” See A225 Operating Notes. DO NOT CONNECT PULSER DIRECTLY TO
THE “IN” POST.

2)

DETECTOR CONNECTION: The “DET” post provides a connection point for a detector and its bias
network. A coupling capacitor “C” of adequate voltage rating must be connected between this point and the“IN” post, as shown in the figure. A bias resistor “R” may be connected as shown between “DET” and “HV.”The detector bias voltage is then applied to “HV.” Note that the “IN” post, which is PIN 1 of the A225, must
always be capacitively coupled and is provided only for connection to detector bias networks external to theboard.

3)

POSITIVE INPUT: Jumper JP1 is A225 PIN 5, output ground, and is connected by jumper to the groundplane. To accommodate positive inputs, remove jumper and connect this point to a negative supply. See A225
Operating Notes.

4)

GROUNDING: In some applications it will be desirable to separate the A225 input and output grounds. To
do so, remove jumper and use “JP1” for output ground connection. See A225 Operating Notes.

A225 with A206
1)

GAIN CONTROL: The A206 input connects to potentiometer R5 which attenuates the A225 output.

2)

BIPOLAR PULSE: A jumper is provided in series with the A206 input (PIN 16). For a bipolar output,
replace this jumper with a capacitor, CD of about 20 pF. This value can be adjusted experimentally for
maximum signal to noise ratio for a particular system. It is also necessary to connect RB, 330 kohm, from PIN
3 to ground to re-bias the voltage amplifier for bipolar operation.

3)

GROUNDING: Ground planes for the A225 and A206 are connected in three places. They may be separated
by cutting these lines if separate grounds are required.

4)

POWER: VS = +4 to +25 VDC if the A225 is used alone without the A206
VS = +10 to +18 VDC if the A225 is used together with the A206

Amptek Inc. 14 DeAngelo Drive, Bedford, MA 01730-2204 USA
Tel: +1 781 275-2242

Fax: +1 781 275-3470

Email: sales@amptek.com

http://www.amptek.com