Here is a simple
triangle/squarewave generator using a common 1458 dual op-amp that can
be used from very low frequencies to about 10 Khz. The time interval for
one half cycle is about R*C and the outputs will supply about 10
milliamps of current. Triangle amplitude can be altered by adjusting the
47K resistor, and waveform offset can be removed by adding a capacitor
in series with the output.