Amplifiers – Signal feedback – Amplifier in signal feedback path
Patent
1977-06-09
1978-10-31
Mullins, James B.
Amplifiers
Signal feedback
Amplifier in signal feedback path
328151, 330259, 330261, 330296, H03F 108
Patent
active
041237226
ABSTRACT:
A sample and hold circuit is disclosed which employs a matched pair of operational amplifiers as a decoupling circuit to isolate the output of the sample and hold circuit from the sampling capacitor. Prior art decoupling circuits employ a simple isolation amplifier which has a tendency to charge the sampling capacitor with the isolation amplifier input bias and leakage currents. The disclosed decoupling circuit employs one of a pair of matched operational amplifiers as a compensation circuit to dynamically generate the bias and leakage currents found at the input of the other operational amplifier, which is employed as the sample and hold isolation amplifier. Thus, the net quiescent current into the input of the decoupling circuit is zero, thereby eliminating the capacitor charging problem of prior art isolation amplifiers.
REFERENCES:
patent: 3461396 (1969-08-01), Harris
patent: 3564301 (1971-02-01), McGhee et al.
patent: 3633004 (1972-01-01), James et al.
patent: 3775692 (1973-11-01), Azegami
Delarue et al., "Circuit Presenting a High Input Impedance," IBM Technical Disclosure Bulletin, v. 19, No. 11, Apr. 1977, pp. 4221-4222.
Choice, "Series-Connected Op Amps Null Offset Voltage," Electronics, Mar. 27, 1972, p. 92.
Maillet, "Sample and Hold Circuit," IBM Technical Disclosure Bulletin, vol. 19, No. 2, Jul. 1976, pp. 536-537.
Naylor, "Digital and Analog Signal Applications of Operational Amplifiers," IEEE Spectrum, May 1971, pp. 79-87.
Bell Telephone Laboratories Incorporated
Graziano James M.
Mullins James B.
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