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.

Features

  • Small Size (16 Pin Dual In-Line Package) allows mounting close to the detector.
  • Power required is typically 12 mW.
  • Single power supply voltage.
  • Low noise.
  • Both Pulse Height Analysis and Pulse Counting mode of operation.
  • High Reliability.
  • One year warranty.

a206 voltage amplifier/discriminator

a206 typical application

Typical Application

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

Voltage Amplifier

Gain 10x nominal, non inverting
Input polarity 1) 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 range 65% of Vs
Ac Output Impedance 20 ohm
Integral Nonlinearity at full output < 0.5%

Discriminator

Input Polarity Positive or Bipolar
Output pulse Positive; 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 time 20 ns
Reference voltage Pin 11, Vr; Range: +4.5 to +5.5 VDC (impedance > 2 Mohm)
Variable voltage Pin 10, Vv; (Vv < Vr)
Discrimination Level Vr – Vv (impedance > 2 Mohm)

General

Operating Voltage +10 to +18 VDC
Operating Current 0.8 mA quiescent @ 15 V
Temperature -55 to +70 ºC operational
Package 16 Pin Dual In-Line (Metal)
Screening Amptek High Reliability
Warranty One year

Pin configuration

a206 pin configuration

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

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.

a206 test circuit
A temperature stable voltage reference should be used.

PC236 Test Board for the A203 with the A206

The PC236 is a printed circuit board designed to facilitate testing of the A203/A206 system. It provides the test circuit for the charge sensitive preamplifier, as well as the voltage references for the discriminator. All components are laid out on a ground plane in order to minimize noise and external pickup.

pc236 layout

PC236 Test Board Layout

pc236 schematic

PC236 Test Board Schematic

PC25 Test Board for use with the A206 and A225

pc25 layout
PC25 test board for the A225 with the A206. 2.625 in x 1.750 in (6.67 cm x 4.45 cm)

THE A-203/A-206 Complete System and Typical Waveforms

a203/a206 complete system

A203/A206 Complete System

a203 waveform csp
Horizontal Scale: 10 µs/div
Vertical Scale: 10 mV/div
Top Trace: Input to test capacitor -22 mV = 1 MeV(Si)
Bottom Trace: Output of CSP (A203, Pin 13)
a203 waveform sa
Horizontal Scale: 500 ns/div
Top Trace: Unipolar output of SA (A203, Pin 8)
Vertical Scale: 50 mV/div
Bottom Trace: Bipolar output of SA (A203, Pin 9)
Vertical Scale: 100 mV
a206 waveform
Horizontal Scale: 2 µs/div
Vertical Scale: 5 V/div
LLD Output-Positive (A206, Pin 9)

The A225/A206 High Resolution System and Typical Waveforms

a225 and a206

a225 waveform a225 waveform 2

A206 Mechanical Diagram

16 pin dip mechanicals