With an oscillator circuit with a frequency sweep function, a first counter counts a reference clock for a number of counts that corresponds to a digital first setting signal, and generates a first count completion signal which is asserted on completion of the count. According to another aspect, the voltage and current of the switch circuits are monitored to determine switch position as well as overall circuit status. At least one of the operational amplifiers includes two or more cascaded amplifier stages and one or more bypass amplifier stages.