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a206 photo - 14k

Model A206 is a Voltage Amplifier/Low level Discriminator developed especially for instrumentation employing solid state detectors, proportional counters, photomultipliers or any charge producing detectors in the pulse height analysis or pulse counting mode of operation.

While this unit was specifically designed for satellite instrumentation, the following unique characteristics make them equally useful for space, laboratory and commercial applications:


Typical Application

Specifications (Vs = +15 V, T = +25 ºC)

Voltage Amplifier

Gain10x nominal, non inverting
Input polarity1) Positive Unipolar; Dynamic range: 85% of Vs
2) Bipolar; If a bipolar input is used, an external resistor (Rb = 330 K ) must be connected between Pin 3 and ground. Dynamic range: 65% of Vs
Dynamic range65% of Vs
Ac Output Impedance20 ohm
Integral Nonlinearity at full output< 0.5%


Input PolarityPositive or Bipolar
Output pulsePositive; 5 µs wide; 90% of Vs.
The output pulse width can be increased by the addition of an external capacitor (1 to 10 pF) between Pins 6 and 8.
Rise time20 ns
Reference voltagePin 11, Vr; Range: +4.5 to +5.5 VDC (impedance > 2 Mohm)
Variable voltagePin 10, Vv; (Vv < Vr)
Discrimination LevelVr - Vv (impedance > 2 Mohm)


Operating Voltage+10 to +18 VDC
Operating Current0.8 mA quiescent @ 15V
Temperature-55 to +70 ºC operational
Package16 Pin Dual In-Line (Metal)
ScreeningAmptek High Reliability
WarrantyOne year

Pin configuration

Pin 1Ground and Case
Pin 2No Connection
Pin 3Bipolar Input Bias
Pin 4Vs Amplifier (+10V to +18V)
Pin 5Vs Discriminator (+10V to +18V)
Pin 6Discriminator Pulse Width Adjust
Pin 7No Connection
Pin 8Discriminator Pulse Width Adjust
Pin 9Discriminator Output
Pin 10+Vv variable (Vv < Vr)
Pin 11+Vr reference (+4.5 to +5.5 VDC)
Pin 12Discriminator Input
Pin 13Amplifier Output
Pin 14No Connection
Pin 15No Connection
Pin 16Amplifier Input

Test Boards for the A206

PC-236 Test Board for use with A206 and A203

PC-236 test board layout. 2.625 in. x 1.750 in. (6.67 cm x 4.45 cm)

pc236 schematic
PC-236 test board schematic

PC-25 Test Board for use with the A206 and A225

pc25 test board
PC-25 test board for the A225 with the A206. 2.625 in. x 1.750 in. (6.67 cm x 4.45 cm)

PC-25 Specifications in PDF format (48k)

Operating Notes

The A206 has two parts:
1) A matching Voltage Amplifier (VA) to the A203 or A225
2) A Lower Level Discriminator (LLD)

The output of the VA is NOT internally connected to the LLD. Pin 13 MUST be connected to Pin 12 if the LLD is to be used.

Power to the VA and LLD is provided separately in order to provide maximum flexibility for independent operation. However, for normal operation Pins 4 and 5 should be connected to Vs.

The VA has an internal input coupling capacitor and no other external capacitor is needed when connecting to either unipolar or bipolar outputs of the A203 or the A225.

If the output of the VA (Pin 13) is to be connected to external circuitry it MUST be coupled with an external capacitor. This output can drive several feet of unterminated coaxial cable.

For bipolar input pulses to the VA connect a 330 kohm resistor from Pin 3 to ground. This biases the amplifier for maximum dynamic range.

The LLD requires a reference voltage Vr and a variable voltage Vv. Set Vr at a level between +4.5 and +5.5 Volts and Vv to a lower voltage than Vr. The Difference, Vr-Vv, is the discrimination level at which the unit will trigger. For example, if Vr = +5 V and Vv = +3.5 V, any pulse of amplitude greater than +1.5 V will trigger the discriminator.

The LLD output pulse is typically a 5 µs wide positive pulse. A wider pulse can be obtained by connecting a capacitor (1 to 10 pF) between Pins 6 and 8. Leave these pins unconnected if the standard pulse width is acceptable.

A typical circuit to provide bias to the LLD is shown below.

A temperature stable voltage reference should be used.

The A225/A206 High Resolution System and Typical Waveforms

The A203/A206 Complete System and Typical Waveforms

Horizontal Scale: 10Ás/div
Vertical Scale: 10mV/div
Top Trace: Input to test capacitor -22mV = 1 MeV(Si)
Bottom Trace: Output of CSP (A-203, Pin 13)

Horizontal Scale: 500ns/div
Top Trace: Unipolar output of SA (A203, Pin 8)
Vertical Scale: 50mV/div
Bottom Trace: Bipolar output of SA (A203, Pin 9)
Vertical Scale: 100mV

Horizontal Scale: 5V
Vertical Scale: 2Ás
LLD Output-Positive (A206, Pin 9)

A-203 & A-206 Specifications in PDF format (1.4 Megs)

PC-25 Specifications in PDF format (48k)

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Revised September 8, 2003