Function generator

As the output voltage reaches upper or lower limits, the charging or discharging is reversed using a comparator, producing the linear triangle wave.

Sawtooth waves can be produced by charging the capacitor slowly with low current, but using a diode over the current source to discharge quickly - the polarity of the diode changes the polarity of the resulting sawtooth, i.e. slow rise and fast fall, or fast rise and slow fall.

A 50% duty cycle square wave is easily obtained by noting whether the capacitor is being charged or discharged, which is reflected in the current switching comparator output.

Two such walking ring counters are perhaps the simplest way to generate the continuous-phase frequency-shift keying used in dual-tone multi-frequency signaling and early modem tones.

They use direct digital synthesis (DDS) techniques to generate any waveform that can be described by a table of amplitudes and time steps.

Examples are the Exar XR2206[7] and the Intersil ICL8038 integrated circuits[citation needed], which can generate sine, square, triangle, ramp, and pulse waveforms at a voltage-controllable frequency.

An electronic circuit element that provides an output proportional to some mathematical function (such as the square root) of its input; such devices are used in feedback control systems and in analog computers.