As hgmjr wrote, the blue arrow points to the input of the circuit.
But to explain more fully, the input is measured in respect with the circuit's ground, or 0v reference. The round ball that is connected via a line to the three horizontal slashes is the ground.
If you need more explanation, please reply stating as to what you are in doubt about.
since i'm trying to simulate it, there is an error on that part.. can you give me a more useful software in simulating circuits.. by the way i'm using Multisim..
Does Multi-Sim have a model for the transconductance amplifier the old CA3080A?
The old CA3080A is obsolete and has not been made for many years. I don't think you can buy one anywhere.
is that so??? so even i can make it worked, i will have a hard time to find that op-amp...
by the way, do you a function generator schematic??or can you help me to make better improvement in my schematic??
i want to know how can i adjust the frequency and the amplitude of the signals generated...
R1 and C1 adjust the frequency. The following op amp integrators shape the waveforms. As the frequency goes up the amplitude will go down, as integrators are basically low pass filters. By the time you hit the high end the signal will be very small indeed.