Browse Prior Art Database

High Speed Integrator

IP.com Disclosure Number: IPCOM000077347D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Mueller, FE: AUTHOR

Abstract

A high-speed integrator which provides a ramp output, slope proportional to the input voltage V1 is shown in Fig. 2.

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High Speed Integrator

A high-speed integrator which provides a ramp output, slope proportional to the input voltage V1 is shown in Fig. 2.

It is desirable to have the emitter voltage of transistor Q1 equal to zero, such that the current through resistor R1 is directly proportional to the input voltage V1. However, the emitter voltage is equal to the reference voltage VR minus the base-emitter voltage drop of transistor Q1. The base-emitter voltage is a logarithmic function of the current passing through transistor Q1. Therefore, for any given input voltage V1 there exists a unique reference voltage, such that the combination of the reference and the base-emitter voltage drops of transistor Q1 would yield a resulting emitter voltage of zero. As can be seen in Fig. 1, with a fixed reference voltage, the ramp output voltage slope is not proportional to the input voltage V1, since the logarithmic function of the base-emitter voltage causes the emitter voltage, VE, to be a nonzero value, except for one unique case.

Fig. 2 shows a modification of Fig. 1, whereby the emitter voltage VE is maintained at zero volts for all values of input voltage V1. The operational amplifier A will adjust the bias voltage to the base of transistor Q1, such that the emitter voltage VE will always be equal to zero. It should be noted that the operational amplifier is fast enough to respond to changes in V1, for proper adjustment of the base voltage allowing the ramp slope output to be a li...