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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 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 TO 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.

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.

A111F Specifications in PDF format (436 k)

Revised February 13, 2003