Gain control in amplifiers or frequency changers without distortion of the input signal

HELECTRICITY H03Electronic circuits H03GCONTROL OF AMPLIFICATION

H03G3/00Gain control in amplifiers or frequency changers without distortion of the input signal

H03G3/001Digital control of analog signals H03G3/002Control of digital or coded signals H03G3/004Control by varying the supply voltage H03G3/005Control by a pilot signal H03G3/007Control dependent on the supply voltage H03G3/008Control by switched capacitors H03G3/02Manually-operated control H03G3/04in untuned amplifiers H03G3/06having discharge tubes H03G3/08incorporating negative feedback H03G3/10having semiconductor devices H03G3/12incorporating negative feedback H03G3/14in frequency-selective amplifiers H03G3/16having discharge tubes H03G3/18having semiconductor devices H03G3/20Automatic control H03G3/22in amplifiers having discharge tubes H03G3/225controlling or controlled by the (local) oscillators of a (super)heterodyne receiver H03G3/24Control dependent upon ambient noise level or sound level H03G3/26Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise H03G3/28in frequency-modulation receivers; in angle-modulation receivers H03G3/30in amplifiers having semiconductor devices H03G3/3005in amplifiers suitable for low-frequencies H03G3/301the gain being continuously variable H03G3/3015using diodes or transistors H03G3/3021by varying the duty cycle H03G3/3026the gain being discontinuously variable H03G3/3031using switched capacitors H03G3/3036in high-frequency amplifiers or in frequency-changers H03G3/3042in modulators, frequency-changers, transmitters or power amplifiers H03G3/3047for intermittent signals H03G3/3052in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/3057using at least one diode as controlling device H03G3/3063using at least one transistor as controlling device, the transistor being used as a variable impedance device H03G3/3068Circuits generating control signals for both R.F. and I.F. stages H03G3/3073Circuits generating control signals when no carrier is present, or in SSB, CW or pulse receivers H03G3/3078Circuits generating control signals for digitally modulated signals H03G3/3084in receivers or transmitters for electromagnetic waves other than radiowaves H03G3/3089Control of digital or coded signals H03G3/3094in parametric amplifiers H03G3/32the control being dependent upon ambient noise level or sound level H03G3/34Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals H03G3/341Muting when no signals or only weak signals are present H03G3/342Muting when some special characteristic of the signal is sensed which distinguishes it from noise H03G3/344Muting responsive to the amount of noise (noise squelch) H03G3/345Muting during a short period of time when noise pulses are detected H03G3/347dependent on the rate of noise pulses H03G3/348Muting in response to a mechanical action or to power supply variations