Method and apparatus for amplifying a signal and test device using same
First Claim
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1. A test device, comprising:
- a first test lead;
a second test lead, the first and second test leads configured to receive an input voltage applied across the first and second test leads;
an output voltage generator having a first input coupled to the first test lead, a second input coupled to a first fixed voltage, a first output coupled to the second test lead, and a second output coupled to a second fixed voltage, the output voltage generator configured to provide to the second test lead and the first output of the output voltage generator a voltage having a magnitude corresponding to a difference between the magnitude of the first fixed voltage and the magnitude of the input voltage;
a processing circuit coupled to the first and second outputs of the output voltage generator, the processing circuit configured to provide an output signal indicative of a voltage across the first and second outputs of the output voltage generator; and
a display coupled to receive the output signal from the processing circuit and configured to provide a visual display indicative of the magnitude of the output signal.
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Abstract
An amplifier circuit is used in a multimeter to amplify signals applied between a pair of test terminals. A voltage applied to one of the test terminals is amplified by a first operational amplifier configured as a voltage follower. An output of the first operational amplifier is applied to an inverting input of a second operational amplifier configured as an integrator. An output of the second operational amplifier is connected to the other of the test terminals. A voltage generated at the output of the second operational amplifier provides an indication of the magnitude and polarity of the voltage applied to the first and second test terminals.
23 Citations
14 Claims
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1. A test device, comprising:
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a first test lead; a second test lead, the first and second test leads configured to receive an input voltage applied across the first and second test leads; an output voltage generator having a first input coupled to the first test lead, a second input coupled to a first fixed voltage, a first output coupled to the second test lead, and a second output coupled to a second fixed voltage, the output voltage generator configured to provide to the second test lead and the first output of the output voltage generator a voltage having a magnitude corresponding to a difference between the magnitude of the first fixed voltage and the magnitude of the input voltage; a processing circuit coupled to the first and second outputs of the output voltage generator, the processing circuit configured to provide an output signal indicative of a voltage across the first and second outputs of the output voltage generator; and a display coupled to receive the output signal from the processing circuit and configured to provide a visual display indicative of the magnitude of the output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of measuring a signal, the method comprising:
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receiving an input voltage across first and second input terminals, wherein the input voltage is the difference between a first voltage at the first input terminal and a second voltage at the second input terminal; generating an output voltage having a magnitude that corresponds to a difference between the magnitude of the input voltage and the magnitude of a fixed voltage; applying the output voltage to the second input terminal thereby causing the voltage at the first input terminal to be equal to the fixed voltage; and providing the output voltage to a processing circuit. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification