GIR on a field effect transistor. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

GIR on a field effect transistor. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Measuring technology

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A common device for radio amateurs is a heterodyne resonance indicator (GIR). Lamp fixtures of this type were inconvenient to handle, as they contained a heavy rectifier and needed to be connected to an AC mains supply. Transistor devices are much lighter, more convenient to use, and therefore enjoy well-deserved success. The advent of field-effect transistors made it possible to create a more sensitive GIR.

A diagram of the simplest GIR on a single field-effect transistor is shown in fig. 1. Dial indicator IP can be with a full deviation current from 50 to 500 μA. Interchangeable coils for different wavelengths can be taken from the circuits of industrial transistor radios. For coils operating in the ranges up to 5-6 MHz, you need to make an average output. On higher frequency bands, the middle output is not required. The GIR is calibrated against a known good factory radio.

GIR on a field-effect transistor
Ris.1

In the case when there is no sensitive pointer device, you can get by with a less sensitive one, for example, with a scale of 0-5 mA. In this case, a DC amplifier is added on one transistor T2 (Fig. 2). The sensitivity of the indicator can be adjusted over a wide range with the potentiometer R5.

GIR on a field-effect transistor
Ris.2

Instead of transistor T1, you can use a field-effect transistor KP302 with any letter index: instead of transistor G2 - MP37 or MP38 with any letter index; diode D1-D2A. With this replacement, it is necessary to reverse the polarity of the battery and diode D1.

Literature

"Practical Wireless", 1972, February.

Publication: N. Bolshakov, rf.atnn.ru

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