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a275

The A275 is a high performance hybrid differential op-amp developed as a pulse amplifier for spaceborne nuclear instrumentation.

Its low power dissipation (15 mW), high slew rate (100 V/µs), and low input noise (4 nV/√ Hz), make it ideal for use in a wide range of op-amp applications. The A275 is packaged in a standard 14-pin hybrid DIP and is also available in a SIP as the A275F.

Features


Applications



Figure 1. - Connection diagram.

Pin Configuration
Pin Function
1 Inverting input
2 Non-inverting input
3 Bias adjust to Pin 4, (R > 3 kohm) Frequency De-Compensation
This resistor will increase the current to the input stage and increase the bandwidth
4 -Vs direct
5 -Vs through 50 ohms
6 Compensation to Pin 7, (C = 0 to 5 pF)
Frequency Compensation to decrease the bandwidth
7 Case and Ground
8 Output through 50 ohms
9 Output direct
10 +Vs through 50 ohms
11 +Vs direct
12,13,14 Compensation (leave open for gain < 10, short for gain > 10)

The A275 is also available in a SIP package as the A275F.

Absolute Maximum Ratings
Supply Voltage ±8 V
Input Voltage ±VS
Operating Temperature -55 C to +125 C
Storage Temperature -65 C to +150 C
Lead Temperature Range (Soldering, 10 sec.) +300 C

Physical
Pacakge 14-pin hybrid DIP, also available in a SIP as the A275F.
Weight 3.8 g

Electrical Characteristics VS = ±6 V, TA = +25 °C
Parameter Symbol Conditions Min Typ Max Units
Input Offset Voltage
Uncompensated/Compensated
VOS     2 5/7 mV
Input Offset Current IOS     0.1 0.6 µA
Input Bias Current IB     1.5 4 µA
Input Capacitance CIN     4   pF
Differential Input Resistance RIN     44   kohm
Common-Mode Input Resistance RIN   >5 8   Mohm
Common-Mode Rejection Ratio CMRR   90 95   dB
Common-Mode Input Range IVR     ±4.5   V
Power Supply Rejection Ratio PSRR     60   dB
Large-Signal Voltage Gain
@5kHz
@5kHz
@10MHz
@10MHz

ALFC
ALF
AHFC
AHF

compensated
uncompensated
compensated
uncompensated

64
72
16
24

66
74
20
28
  dB
Pulse Risetime (AV = 10) trc
tr
compensated
uncompensated
  15
9
22
15
ns
Output Voltage Swing VOP
VON
positive
negative
+4.2
 
+4.4
-5.0

-5.5
V
Open Loop Output Resistance RO     750   ohm
Output Short-Circuit Current IOSC source
sink
  11
-4
  mA
Slew Rate SRP
SRN
positive
negative
65
35
100
40
  V/µs
Input Noise Voltage Density eN     4   nV/√Hz
Supply Current IS   ±1.1 ±1.25 ±1.4 mA
Power Consumption PD     15   mW


Figure 2. - A275 gain & phase


Figure 3. - A275 pulse characteristics
Upper: Input pulse
First output: 3 pole
Second output: 5 pole

Circuit Layout Considerations

Due to the high bandwidth of the A275, care should be taken in circuit layout. In general, ground plane construction is recommended. Input and output lines should be well separated and in most cases shielding will be necessary. Grounding the physical case of the A275 (in addition to Pin 7) to the ground plane can be used to avoid oscillations or electronic pick-up.

PC-275

The A275 can be tested as a shaping amplifier by using the circuit shown below.
The PC-275 Test Board accommodates three (3) A275s and a BLR1 and produces a 5-pole pulse with 1 s risetime (2.3 s peaking time).

pc275 layout
Figure 4. PC-275 layout. Dimensions: 3.5 in X 1.75 in (88.9 mm X 44.45 mm)

pc275 schematic
Figure 5. The A250 connected to a solid state detector with 5-pole shaping and active baseline restoration (BLR1). The PC-275 Schematic begins at the output of A250.


Figure 6. - General case for 3 and 5-pole response for different peaking times (TP)


See also the A275F SIP

A-275 Specifications PDF (584 k)
PC-275 Test Board Specifications PDF (300 k)


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Revised May 23, 2010