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Discretely constructed HF amplifier LM703


Like the CA3028A, the LM703 contains a differential amplifier, but it is slightly different. It was often used in receiver technology as an RF amplifier. In addition, it could be found in some commercially manufactured hi-fi radio receivers of the 1970s in the 10.7MHz IF stages of the VHF section. Here is the circuit of the recreated LM703.

In order to achieve a higher cut-off frequency, RF transistors with a higher transit frequency can be used. However, it is also important that the structure is as compact as possible and with short lines. The component side of the board should have a conductive ground surface.

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