VGA with Voltage Feedback, Constant Bandwidth and a High Degree of Independence Between Amplifier and Gain Controller

The following paper is devoted to an amplifier with gain control (Variable Gain Amplifier). role of amplification and addressed separately from the very beginning, achieve greatest possible independence required parameters both for itself (gain size, bandwidth, noise figure) controller (energy consumption control, distortion). core consists operational voltage feedback (VFB) in inverting circuit, which a regulator executed diode bridge connected parallel. analysis simplified circuit model shows that it obtain variable-gain maintains its bandwidth. continuous only one element, variable resistance, sufficient control. This resistance can be achieved by number components, either rheostat, FET transistor channel (the related GND, advantageous), or resulting dynamic bridge. Continuous element preserving bandwidth VFB unique authors are unaware any other similar solution. If maximum required, disconnected does not contribute VGA amplifier. Because between output input, because input current controlled, processes portion amplifier, thus preventing more noticeable distortion. distortion further suppressed due simultaneous action four diodes bridge, whose characteristics reciprocal signal path. presented construction relatively simple topic microelectronic structures, but also applications discrete components. connection as follows: change 0 20 dB, constant 7 MHz, distance III. harmonics min. 30 dB at 0.5 V, power spectral density 25 ∙10-15 V2Hz-1.