Low noise good precision magnetic head amplifier (AD797) circuit

Published:2011/5/10 2:23:00 Author:TaoXi | Keyword: Low noise, good precision, magnetic head amplifier | From:SeekIC

The low noise good precision magnetic head amplifier (AD797) circuit is as shown. These three circuits have different input modes. In figure (a), the input signal with the single-ended input mode adds to the current source-type differential amplifier circuit which is composed of the transistors, and this circuit outputs the signal with differential amplifier mode to the op amp AD797's two input ports (pins 2,3). This circuit uses the differential amplifier which is composed of the transistor structure with excellent performance, so this circuit has high signal to noise ratio (S/N) and can process the signal with larger dynamic range. In figure (a), the three transistors are 2SC3329, VT3 is the constant current tube, VT1 and VT2 are the differential amplification tube. Add the 20kΩ feedback resistor and the 270pF compensation capacitor between the op amp AD797's output port (pin 6) and VT2's base pin. Feedback resistor of the 20Ω resistance from VT2 to ground and the 20kΩ feedback resistor decide the voltage gain, the 270pF compensation capacitor improves the stability of the circuit. You need to add two resistances (10μF electrolytic capacitor and 0.1μF organic synthetic membranes capacitance) between the positive and negative power supply terminals (pin 7,4) and the ground as the decoupling capacitor. You can filter the high-frequency interference and the low-frequency interference in this way.



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