chips like 8038 are not arbitrary function generators. they simply generate predefined functions using VFO and signal shaping/conditioning.
arbitrary function generators can produce any shape of signal user wants (programs it). simple approach is to have oscillator of variable frequency (clock) driving counter. counter outputs are used to address memory location (incrementing/decrementing). value from addresses memory location is converted to analog signal (DAC). memory can be (E)EPROM for example but this is not convenient way of changing program (wave shape). it is common to use MCU for example. this way MCU can communicate with computer to receive new programs.
No not the oscillator or VCO part the waveshaping stage AFTER the VCO or oscillator because all a oscillator or VCO does is produce square,sine,triangle and then Waveshaping or signal shaping stages,circuits,blocks change it
they only make basic changes (saw tooth, rectangle, etc.).
it is impossible to make analog device that will allow any desired signal shape on the output. this is why arbitrary function generators are using digital technology and lookup tables. you can make simple analog generator using oscilator, counter(s) such as 4017 and connect potentiometer to each output. connect all wipers through diode to comon point and amplify signal with an opamp for example. with each potetiometer you can adjust amplitude of the output signal for one single step. depending on number of steps you could have more or less complex output.
So you saying to hook up like 4 function generators and get a Summing amp or mixer to sum or mix different sine/triangle/square waveforms to create complex waveforms?
The schematics for the ICL8038, MAX038 and XR2206 function generator IC circuits are in their datsheets. Frequently an entire project is shown with parts lists having manufacturer's part numbers and even a pcb layout. They also describe how they work with good detail.
Take a square wave, a perfect one from a digital divider, and feed it through an 8th-order switched-capacitor Butterworth lowpass filter IC and the resulting sinewave is nearly perfect with only about 0.05% distortion.
Take a clock frequency that is 10 times higher than the output and clock a CD4018 Johnson "walking-ring" Counter with 4 output resistors to make a stepped sinewave that is actually oversampled. Feed it through an 8th-order switched-capacitor Butterworth lowpass filter IC and the resulting sinewave is perfect with unmeasurable distortion, like I have in my audio generator. The counter and resistors perform like the ones in Harry's Eprom circuit. :lol: