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 DIAGRAM
A111F PIN CONFIGURATION
Pi n 1
Pi n 2
Pins 3 & 4
Pi n 4
Pi n 5
Pi n 6
Weight: 1.75 grams
Input
Ground & Case
Threshold Adjust
Analog Monitor
V (+4 to +18 VDC)
Output
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 & 4 can be
achieved by an RC feedback as shown below.
C
3
1
R
4
Apart from unit to unit variation, the discrimination levels will be as follows:
1)
2)
Shorting out Pins 3 and 4 will result in x10 increase of nominal threshold:
(5 x 10
4
electrons) x 10 = 5 x 10
5
electrons.
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= 5k
C = 4.7 pF : x 40
R= 2k
C = 6.8 pF : x 88
Intermediate values can be obtained by adjusting the value of R.
B) Decreasing the Threshold of A111F:
Decreasing the threshold of the A111F beyond the nominal 5 x 10
4
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 10
4
electrons.
Please refer to the A111 specifications for further information.
AMPTEK,
INC.
6 DE ANGELO DRIVE, BEDFORD, MA 01730-2204 USA
TEL: +1 (781) 275-2242
FAX: +1 (781) 275-3470
email: sales@amptek.com
www.amptek.com
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