What influences output frequency in sweep generator?

[redhat]

sweep generator

i want to make a sweep frequency generator in the range of 2MHz (center frequency is 1MHz) using CD4046 VCO , i want to know what are the things that influence the output frequency?the VCOin should be the voltage that controls the output frequency and the range can be selected by changing Cext and R1,is that correct?

 

[IanP]

Re: sweep generator

That is correct.
R1, C1 and Vin are used to control output frequency..
(R2=∞)

 

[redhat]

Re: sweep generator

i have another question,what happens if i reverse the polarity of the VCOin i.e. the input is -5v for example ,the graph in the datasheet doesn't have -ve voltage values.

 

[IanP]

Re: sweep generator

CMOS and TTLs were designed to operate only in positive ranges from 0V to Vdd/Vcc.
What will happen if you apply negative voltage to Vin?
Most likely you will destroy the IC..