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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/Ö 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

• Power 15 mW
• Slew Rate 100 V/µs
• Input Noise 4 nV/ÖHz
• Stable DC Operation
• 200 MHz Gain-Bandwidth Product
• High Reliability Screening
• Unity Gain Stable

Applications

• Space Instrumentation
• Portable Instrumentation
• Nuclear Instrumentation
• Precision Active Filter Design
• Pulse Shaping

Figure 1. - Connection diagram.

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

Electrical Characteristics VS = ±6 V, TA = +25 °C
Parameter	Symbol	Conditions	Min	Typ	Max	Units
Input Offset Voltage	VOS			2	5	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/ÖHz
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 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 (T_P)

See also the A275F SIP

A-275 Specifications in PDF format (584 k)

Revised January 23, 2006