Compensated Temperature Variable Resistor

摘要

A front-end circuit for measurement devices, for example oscilloscopes or digitizers, may implement DC gain compensation using a programmable variable resistance. A MOS transistor may be configured and operated as a linear resistor with the ability to self-calibrate quickly, while compensating for temperature variations. An integrated CMOS-based variable resistor may be thereby used for an analog adjustable attenuator. Master and slave CMOS transistors may be operated in linear mode, and temperature effects on the linear transistors may be compensated for by using an integral loop controller (current controller) configured around the master MOS transistor. Circuits implemented with the compensated variable resistance have a wide range of adjustment with a control voltage, and may be used in the front-end (circuits) of an oscilloscope or digitizer, or in any other circuit and/or instrumentation benefitting from an adjustable attenuator.

主权项

1. A resistance circuit comprising:
a first transistor device configured to operate in linear mode, and having an operative resistance value representative of a specified nominal resistance value; a second transistor device having device characteristics commensurate with characteristics of the first transistor device, wherein the second transistor device is configured to operate in linear mode, and have an operative resistance value representative of the specified nominal resistance value; and control circuitry configured to:
cause the operative resistance value of the second transistor device to return to the specified nominal resistance value when the operative resistance value of the second transistor device drifts away from the specified nominal resistance value due to changes in temperature; andcontrol the first transistor device by a control signal generated according to operation of the second transistor device, causing the operative resistance value of the first transistor device to return to the specified nominal resistance value when the operative resistance value of the first transistor device drifts away from the specified nominal resistance value due to changes in temperature.