Device and method for testing common-mode input impedance of operation amplifier

An operational amplifier and common-mode input technology, which is applied in the field of semiconductor testing, can solve the problem of not testing the common-mode input impedance of operational amplifiers.

CN101995519AInactive Publication Date: 2011-03-30TIANSHUI HUATIAN MICROELECTRONICS
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2011-03-30
Estimated Expiration
Not applicable · inactive patent

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Abstract

The invention relates to a device and method testing common-mode input impedance of an operation amplifier. The device comprises a circuit formed by connecting a resistor with a switch in parallel, wherein one end of the parallel circuit is serially connected with an alternating-current signal source. When the common-mode input impedance of the operation amplifier is tested, a resistor is adoptedto form the parallel circuit with the switch, wherein the resistance value of the resistor is the same as the common-mode input impedance design value of the operation amplifier to be tested or is lower than the same by one magnitude order, the alternating-current signal source, the parallel circuit and the operation amplifier to be tested are sequentially connected, the switch is switched on oroff, and output voltages VL1 and VL2 of the operation amplifier to be tested are respectively tested; and the input resistance of the operation amplifier to be tested is figured out through a formula, and the common-mode input impedance of the operation amplifier to be tested is figured out according to the input resistance. The method can be used for testing the large-resistance common-mode input impedance of the operation amplifier so that the property of the operation amplifier is accurately displayed.
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Description

technical field

[0001] The invention belongs to the technical field of semiconductor testing, and relates to a test device for common-mode input impedance of an operational amplifier, and also relates to a method for testing the common-mode input impedance of an operational amplifier by using the test device. Background technique

[0002] The common-mode input impedance of operational amplifiers is a very important parameter to measure the performance of operational amplifiers, especially for high-precision operational amplifiers, whose common-mode input impedance often reaches hundreds of GΩ. Such a large resistance value is difficult to test, and it is generally only listed as a reference parameter without testing. However, there is currently no effective method for testing the common-mode input impedance of an op amp. Contents of the invention

[0003] In order to overcome the above-mentioned problems in the prior art, the object of the present invention is to provide ...

Examples

Embodiment

[0051] Referring to the design value of the common-mode input impedance of the operational amplifier op07, select a resistor 2 whose resistance value is the same order of magnitude as the design value of the common-mode input impedance of the operational amplifier, connect the selected resistor 2 and switch 3 in parallel to form a parallel circuit, and connect the AC signal source 1 , The parallel circuit and the operational amplifier op07 are connected in series in sequence, the power is turned on, the switch 3 is closed, and the output voltage V at the output terminal of the operational amplifier op07 is measured with a six-and-a-half-digit high-precision digital voltmeter 34401A L1 ; Then, switch off switch 3, and measure the output voltage V at the output terminal of the operational amplifier op07 with a six-and-a-half-digit high-precision digital voltmeter 34401A L2 ; via the formula

[0052]

[0053] Calculate the input resistance of the operational amplifier op07 r ...