Bulgarian Signal Function Generator

This DIY design from Bulgaria shows a versatile function generator. The circuit uses an Intersel IC ICL8038. Although it is an old design, this chip performs well and is still available (I ordered two of them at Kent Electronics for under 3 euro each). You can use the output signal for measurements or to modulate your transmitter under test.

The ICL8038 waveform generator is a monolithic integrated circuit capable of producing high accuracy sine, square, triangular, sawtooth and pulse waveforms with a minimum of external components. The frequency (or repetition rate) can be selected externally from 0.001Hz to more than 300kHz using either resistors or capacitors. FM (frequency modulation) and sweeping can be accomplished with an external voltage. The ICL8038 is fabricated with monolithic technology, using Schottky barrier diodes and thin film resistors, and the output is stable over a wide range of temperature and supply variations.

I found a simple design at http://www.constructor.bg/mk/testgen.htm

Google translator was able to convert the Bulgarian text to Dutch for me.  This made it possible to understand the labels.

The circuit uses + and - 12 VDC which you can produce with an 7812 and a 7912 voltage regulator.

Controls are as follows:

Selector switch to R3, R4, R9: Waveform
Selector switch to C3...C7:Frequency Adjustment, coarse
P5 / P1 : Frequency Adjustment, fine
P6 : Output level
P2: Symmetry
P3, P4: Linearity

Component values:

Resistors:  R1 - 56 , R2 - 12 к , R3 - 10 к , R4 - 56 к , R5 - 10 к , R6 - 2.4 к , R7 - 2.4 к ,
R8 - 7.72 M ( 4.3 M + 3.3 M + 120 к ), R9 - 33к , R10 - 18 к , R11 - 20 к , R12 - 680 ,
R13 - 220   
Potmeters: P1 - 1 к , P2 - 1 к , P3 - 100 к , P4 - 100 к , P5 - 10 к , P6 - 100 к .
Capacitors: С3 - 200 pF, С4 - 2.2 nF, С5 - 22 nF, С6 - 220 nF, С7 - 2.2 uF, С8 - 100 nF,  С11 - 100 uF.
Semiconductors: Т3 – 2N3904, Т4 – 2N3904

Generator under development