[Tianjin University of Technology] Differential amplifier circuit tester_Wu Jin

This differential amplifier circuit tester is composed of a single-chip microcomputer control module, a DDS signal generation module, a differential signal conversion module, a differential amplifier circuit and a signal detection circuit. The DDS signal generation module generates a stable sinusoidal signal with adjustable frequency, phase, and amplitude. The microcontroller DAC generates a common mode signal. The two signals are converted into a differential mode signal with a common mode through the AD8138 single-ended to differential module. Input into the differential amplifier circuit composed of 9013, the signal is amplified and then input to the AD8130 differential to single-ended module to become a single-ended signal. Then use AD937 to directly measure the effective value of the output single-ended signal, and you can obtain information such as the amplification factor of the differential amplifier circuit. The frequency sweep method can also be used to obtain the amplitude-frequency characteristic curve of the amplifier circuit, and then directly obtain the upper limit cutoff frequency.

Working principle: With AD8138 chip as the core and packaged as SOP8, AD8138 can be used as a single-ended to differential amplifier or a differential to differential amplifier. Fabricated on Analog Devices' proprietary XFCB bipolar process, the device has a -3 dB bandwidth of 320 MHz and provides differential signaling with the lowest harmonic distortion among available differential amplifiers. The AD8138 has a unique internal feedback feature that provides balanced output gain and phase matching to suppress even-order harmonics. Internal feedback circuitry minimizes any gain errors associated with external gain setting resistor mismatches.

Function: Convert single-ended signals into differential signals, and can add common-mode signals at the same time.