The paper analyses five basic types of chopper circuit suitable for converting low-level direct voltages to alternating voltages. Three of them are capacitance coupled and two are transformer coupled; all have resistive loads.Both transformer-coupled circuits have make-before-break (overlap) contact action and incorporate a stopper resistor. If the overlap is small, this arrangement provides input resistances which approach those of the equivalent buffered underlap circuits, together with several other advantages.Expressions are derived for gain, input resistance and optimum stopper resistance in terms of the component values.