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 Input Pi n 2 Ground & Case Pins 3 & 4 Threshold Adjust Pi n 4 Analog Monitor Pi n 5 V (+4 to +18 VDC) Pi n 6 Output Weight: 1.75 grams 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. 3 C 1 R 4 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= 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 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. AMPTEK, INC. 6 DE ANGELO DRIVE, BEDFORD, MA 01730-2204 USA TEL: +1 (781) 275-2242 FAX: +1 (781) 275-3470 email: [email protected] www.amptek.com