PREAMPLIFIER OF INTERMEDIATE FREQUENCY Russian patent published in 2008 - IPC H03F3/189 

FIELD: radio engineering, in particular, may be used as preamplifier of intermediate frequency, and also in frequency transformers which contain double balance mixers of radio-receiving devices with phase suppression of mirror channel frequencies.

SUBSTANCE: in accordance to the invention, constant-current wise the amplifier is enveloped by deep negative check connection, which ensures high stability of operation modes of transistors. From divider on resistors (3 and 4) the signal voltage through negative check connection circuit is sent to primary winding of transformer (7). At secondary winding of transformer (7), negative check connection voltage occurs, which is coupled serially between capacitor (24) and base of transistor (1). Also, signal voltage, read from divider (3 and 4) through negative check connection, and through capacitor (23) is received at resistor (6). As a result of that, negative check connection current is received in point of connection of capacitor (24) and secondary winding of transformer (7). If depth of negative check connection of amplifier is sufficient, its input resistance will be equal to ratio of negative check connection voltage to negative check connection current, which are received at the input of amplifier. Output resistance of amplifier is practically equal to resistance of resistor (5), and, therefore, resistance of load of amplifier, coupled in parallel with resistor (5), does not influence the functioning of amplifier. As a result of operation of negative check connection, transmission coefficient and input resistance of amplifier depend only on parameters of transformer (7) and values of resistances of resistors (3,4 and 6), and output resistance of amplifier is equal to value of resistance of resistor (5). Input resistance of amplifier also does not depend on input resistance of transistor of first cascade of amplifier.

EFFECT: increased efficiency.

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