For my audio amps I needed some small generator just for testing. And I also had MAX038 chip sample. Here is the abstract from datasheet:
The MAX038 is a high-frequency, precision function generator producing accurate, high-frequency triangle, sawtooth, sine, square, and pulse waveforms with a minimum of external components. The output frequency can be controlled over a frequency range of 0.1Hz to 20MHz by an internal 2.5V bandgap voltage reference and an external resistor and capacitor. The duty cycle can be varied over a wide range by applying a Â±2.3V control signal, facilitating pulse-width modulation and the generation of sawtooth waveforms.
Frequency modulation and frequency sweeping are achieved in the same way. The duty cycle and frequency controls are independent.
Sine, square, or triangle waveforms can be selected at the output by setting the appropriate code at two TTL-compatible select pins. The output signal for all waveforms is a 2VP-P signal that is symmetrical around ground. The low-impedance output can drive up to Â±20mA.
Component values are described in MAX datasheet.