Decibel stepper, The stepper presented here makes use of nine positions of a 12-position rotary switch. It is, of course, possible to add the three steps. As usual, the amplification factors are arrived at by connecting a number of resistors in series in the feedback circuit. The resistors used here are for the E-96 series, which enable a fairly accurate approximation of the wanted amplification.
If greater precision is required, combinations of two resistors may be used. This has the drawback, however, that makes before break switch must be used to prevent the output constantly being switched to the supply line.
The bandwidth of the amplifier is determined by the set gain and the gain-bandwidth product of the opamp. If an LF351 is used as shown, the gain bandwidth product is 4 MHz, while the slew rate is 13 V us-1.
Capacitor C1 improves the stability when the amplification factor is large.