The A111F is a high density version of the Amptek A111 Charge Sensitive Preamplifier and Discriminator.
The A111F features a Single In-line Package (SIP).

A111F Mechanical Dimensions
A111F Mechanical Dimensions

A111F Pin Configuration

Pin 1 Input
Pin 2 Ground and Case
Pins 3 & 4 Threshold Adjust
Pin 4 Analog Monitor
Pin 5 V (+4 to +18 VDC)
Pin 6 Output

Weight: 1.6 g with leads cut to 0.100 inch (2.5 mm).

APPLICATION NOTE: A111F THRESHOLD ADJUSTMENT

A) INCREASING THE THRESHOLD OF THE A111F

Increasing the threshold of the A111F beyond the x10 provided by shorting out Pins 3 and 4 can be achieved by an RC feedback as shown below.

A111F threshold

Apart from unit to unit variation, the discrimination levels will be as follows:

  1. Shorting out Pins 3 and 4 will result in x10 increase of nominal threshold: (5 x 104 electrons) x 10 = 5 x 105 electrons.
  2. Shorting out Pins 3 and 4 plus feedback:
    R = 50 k C = 2.2 pF x 17
    R = 20 k C = 3.3 pF x 23
    R = 5 k C = 4.7 pF x 40
    R = 2 k C = 6.8 pF x 88

    Intermediate values can be obtained by adjusting the value of R.

B) DECREASING THE THRESHOLD OF THE A111F:

Decreasing the threshold of the A111F beyond the nominal 5 x 104 electrons can be achieved by adding a resistor from Pin 4 to ground. A 300 ohm resistor will approximately double the sensitivity resulting in a threshold of 2.5 x 104 electrons.

Please refer to the A111 specifications for further information.