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.
Figure 1. - Connection diagram.
|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
|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|
|10||+Vs through 50 ohms|
|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|
|Operating Temperature||-55 °C to +125 °C|
|Storage Temperature||-65 °C to +150 °C|
|Lead Temperature Range (Soldering, 10 sec.)||+300 °C|
|Pacakge||14-pin hybrid DIP, also available in a SIP as the A275F.|
|Electrical Characteristics VS = ±6 V, TA = +25 °C|
|Input Offset Voltage
|Input Offset Current||IOS||0.1||0.6||µA|
|Input Bias Current||IB||1.5||4||µA|
|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
|Pulse Risetime (AV = 10)||trc
|Output Voltage Swing||VOP
|Open Loop Output Resistance||RO||750||ohm|
|Output Short-Circuit Current||IOSC||source
|Input Noise Voltage Density||eN||4||nV/√Hz|
Figure 2. - A275 gain & phase
Figure 3. - A275 pulse characteristics
Upper: Input pulse
First output: 3 pole
Second output: 5 pole
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.
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 µs risetime (2.3 µs peaking time).
Figure 4. PC-275 layout. Dimensions: 3.5 in X 1.75 in (88.9 mm X 44.45 mm)
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)
Revised May 23, 2010