Variable Gain Amplifier Circuit. The op amp variable gain circuit below maintains input impedance over the range of the gain providing a distinct advantage in some instances. The gain can thus be made variable by replacing r1 with a pot and connecting its slider to the inverting terminal of the op amp as shown in the circuit in figure 4 in which the gain can be varied over the range x1 to x101 via rv2.
It provides precise pin selectable gain with a gain range of 11 db to 31 db at 90 mhz bandwidth and a gain range of 9 db to 51 db at 9 mhz bandwidth. The gain of the amplifier then depends on the light falling on the ldr which can be provided by an led. However when the analog signal path is digitally controlled a digital potentiometer might be used to control gain.
High power amplifiers up to 100w.
Applications ranging from ultrasound radar lidar wireless communications and speech analysis have utilized vgas to deliver industry leadi. A voltage controlled amplifier or variable gain amplifier is an electronic device amplifier that varies its gain depending on the applied control voltage cv. Ad603 is a low noise voltage controlled amplifier for radio frequency rf and intermediate frequency if automatic gain control agc systems. The circuit is very simple and only uses one additional component over that of a basic operational amplifier circuit.
