Track and hold circuit with clamp

Details Track and hold circuit with clamp Track and hold circuit with clamp

1998-04-20

2000-02-22

Nuton, My-Trang

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By amplitude

327 96, G11C 2702

Patent

active

060284595

ABSTRACT:
A track-and-hold amplifier circuit capable of increasing hold mode isolation includes an input circuit to buffer an input signal coupled to a switching transistor. A clamping transistor couples to the base of the switching transistor, and a hold capacitor couples between the emitter of the switching transistor and circuit ground. A differential amplifier circuit has a first input for receiving a track signal and a second input for receiving a hold signal. When the differential amplifier circuit receives the track signal, the switching circuit closes to charge the hold capacitor. When the differential amplifier receives the hold signal, the switching transistor opens to store the voltage representative of the input signal on the hold capacitor and the clamping transistor clamps the voltage at the base of the switching transistor. Thus, the base emitter voltage of the switching transistor is zero volts, and the signal held by the hold capacitor is independent of the input signal. In addition, by using level shifters, the voltage clamped at the base of the switching transistor is substantially equal to the voltage held on the hold capacitor.

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patent: 5457418 (1995-10-01), Chang
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patent: 5583459 (1996-12-01), Sone
patent: 5734276 (1998-03-01), Abdi et al.
patent: 5838175 (1998-11-01), Hsieh
Razavi, Behzad, Design of a 100-Mhz 10-Mw 3-V Sample-and-Hold Amplifier in Digital Bipolar Technololgy, IEEE Journal of Solid-State Circuits, vol. 30, No. 7, Jul. 1995, pp. 724-730.
Vorenkamp et al., Fully Bipolar, 120-Msample/s 10-b Track-and-Hold Circuit, IEEE Journal of Solid-State Circuits, vol. 27, No. 7, Jul. 1992, pp. 988-992.
Vorenkamp et al., A 12b 50MSample/s Cascaded Folding and Interpolating ADC, Phillips Composants et Semiconducteurs, Caen, France, 1997 IEEE International Solid-State Circuits Conference (ISSCC97), Session 8/Data Converters/Paper FA 8.2, Feb. 7, 1997.

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