Amplifiers – Bootstrap coupling
Patent
1994-02-28
1995-02-21
Mullins, James B.
Amplifiers
Bootstrap coupling
324123C, 330 76, 330 85, 330112, 330292, 330294, H03F 138, G01R 130
Patent
active
053920015
ABSTRACT:
A capacitively-coupled amplifier circuit includes an amplifier for receiving an input signal via a coupling capacitance and for amplifying the input signal to produce an output signal. A resistor provides a bias voltage to the amplifier. The resistor is bootstrapped using positive feedback with a loop gain of slightly less than one. The bootstrapping causes an increase in the value of the resistor to lower the cut-in (pole) frequency of the amplifier. The bootstrapping or feedback circuit includes a roll-off (pole) at a frequency below the roll-off (pole) frequency of the amplifier. This prevents phase shift in the feedback loop from adversely effecting the high frequency response of the amplifier. The resulting amplifier circuit exhibits a wide passband and excellent low frequency response despite having a capacitively coupled input signal.
REFERENCES:
patent: 5274336 (1993-12-01), Crook et al.
Dragun, "Transistorized Remote Amplifier for the S1-11 Oscillograph, " Instrum. & Exp. Tech. , No. 3, May., Jun. 1970, pp. 948-949.
Horn, "Feedback Reduces Bio Probes Input Capacitance," Electronics, Mar. 18, 1968, pp. 97, 98.
Heumann John M.
Peiffer Ronald J.
Uhling Thomas F.
Hewlett--Packard Company
Mullins James B.
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