Abstract
The design of a circuit of three modules: the former level amplifier (with AGC), after-class amplifier and SCM display and control module. First-class amplifier, with broadband operational amplifiers AD603 two cascade to enlarge the input signal and output to enlarge a certain multiple of the voltage, after-class amplifier reached after more than 8 V of the RMS output. SCM, control and data processing module can be programmed in addition to adjusting the gain amplifier, can also display real-time output voltage RMS. The design uses high voltage-controlled gain devices, a reasonable cascade and impedance matching, negative feedback after the entry-level complementary output stage, and comprehensively improve the gain bandwidth product and output voltage range. Application MCU and digital signal processing technology to gain a preset and control, AGC has good stability, controllable range. Band system as a whole for 1 KHZ ~ 20MHZ, the smallest gain of 0 dB, the biggest gain of 80 dB. Stepping gain for the 1 dB, 60dB gain and below preset time when error is less than 0.2 dB. Distortion of the output voltage is not an effective value of 9.5 V, output 4.5 V ~ 5.5V when, AGC control range of 66 dB
Keywords：AD603, broadband amplifiers, gain, zoom, AGC
