v r and the particular high and low voltage level values referring now to fig4 the analog voltage output of the operational amplifier 36 and the square wave output of the operational amplifier 38 are both illustrated these signals are illustrated relative to a time line as shown referring to the output signal of the operational amplifier 36 as has been previously discussed this amplifier should be a follower of the changing voltage on the variable capacitance capacitor 30 accordingly the output signal of the operational amplifier 36 rises when the variable capacitance capacitor 30 charges due to the output voltage from the operational amplifier 38 being high at a time t o at time t 1 the output voltage of the operational amplifier 36 as applied to the inverting input of the operational amplifier 38 rises to the high voltage limit applied to the noninverting input of the operational amplifier 38 this will cause the output of the operational amplifier 38 to switch low which further lowers the reference voltage applied to the noninverting input of operational amplifier 38 the resulting low voltage at the output of the operational amplifier 36 causes the variable capacitance capacitor 30 to discharge through resistance 40 this prompts the output of the operational amplifier 38 to begin to decrease in value due to the discharging of the variable capacitor 30 when the voltage output of the operational amplifier 36 falls below the low voltage imposed on the noninverting input of the operational amplifier 38 the operational amplifier 38 will switch high again as denoted at time t 2 it is hence to be appreciated that the charging and the discharging of the variable capacitance capacitor 30 as reflected in the voltage following operational.