Precision absolute-value amplifier for a precision voltmeter

Patent · Tue Oct 19 00:00:00 EDT 1982

OSTI ID:5827771

Hearn, W E; Rondeau, D J

Bipolar inputs are afforded by the plus inputs of first and second differential input amplifiers. A first gain determining resistor is connected between the minus inputs of the differential amplifiers. First and second diodes are connected between the respective minus inputs and the respective outputs of the differential amplifiers. First and second FETs have their gates connected to the outputs of the amplifiers, while their respective source and drain circuits are connected between the respective minus inputs and an output lead extending to a load resistor. The output current through the load resistor is proportional to the absolute value of the input voltage difference between the bipolar input terminals. A third differential amplifier has its plus input terminal connected to the load resistor. A second gain determining resistor is connected between the minus input of the third differential amplifier and a voltage source. A third FET has its gate connected to the output of the third amplifier. The source and drain circuit of the third transistor is connected between the minus input of the third amplifier and a voltage-frequency converter, constituting an output device. A polarity detector is also provided, comprising a pair of transistors having their inputs connected to the outputs of the first and second differential amplifiers. The outputs of the polarity detector are connected to gates which switch the output of the voltage-frequency converter between up and down counting outputs.

• DOE Contract Number: AC03-76SF00098
• Assignee: ERA-08-054773; EDB-83-179032
• Patent Number(s): None
• Application Number: ON: DE83018020
• OSTI ID: 5827771
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420800 -- Engineering-- Electronic Circuits & Devices-- (-1989)
440300* -- Miscellaneous Instruments-- (-1989)
47 OTHER INSTRUMENTATION
AMPLIFIERS
DESIGN
ELECTRIC MEASURING INSTRUMENTS
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
EQUIPMENT
FIELD EFFECT TRANSISTORS
MEASURING INSTRUMENTS
RESISTORS
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
TRANSISTORS
VOLTMETERS