OP27GSZ datasheet(18/20 Pages) AD

18 / 20 page

OP27

Rev. F | Page 18 of 20

Capacitor C2 and Resistor R2 form a 2 μs time constant in this

circuit, as recommended for optimum transient response by the

transformer manufacturer. With C2 in use, A1 must have unity-

gain stability. For situations where the 2 μs time constant is not

necessary, C2 can be deleted, allowing the faster OP37 to be

employed.

A 150 Ω resistor and R1 and R2 gain resistors connected to a

noiseless amplifier generate 220 nV of noise in a 20 kHz

bandwidth, or 73 dB below a 1 mV reference level. Any practical

amplifier can only approach this noise level; it can never exceed

it. With the OP27 and T1 specified, the additional noise

degradation is close to 3.6 dB (or −69.5 referenced to 1 mV).

REFERENCES

Lipshitz, S. R, “On RIAA Equalization Networks,” JAES,

Vol. 27, June 1979, p. 458–481.

Jung, W. G., IC Op Amp Cookbook, 2nd. Ed., H. W. Sams

and Company, 1980.

Jung, W. G., Audio IC Op Amp Applications, 2nd. Ed., H. W.

Sams and Company, 1978.

Jung, W. G., and Marsh, R. M., “Picking Capacitors,” Audio,

February and March, 1980.

Otala, M., “Feedback-Generated Phase Nonlinearity in

Audio Amplifiers,” London AES Convention, March 1980,

preprint 1976.

Stout, D. F., and Kaufman, M., Handbook of Operational

Amplifier Circuit Design, New York, McGraw-Hill, 1976.

OP27GSZ Datasheet(PDF) 18 Page - Analog Devices