# 1MHz signal generator

#### maniza_201

Joined Feb 19, 2006
6
how to design a circuit that can generate 1MHz signal?

#### pebe

Joined Oct 11, 2004
626
Originally posted by maniza_201@Mar 1 2006, 09:39 AM
how to design a circuit that can generate 1MHz signal?
[post=14486]Quoted post[/post]​
Sine? Square?

#### moosa

Joined Mar 1, 2006
8
I remember I made something similar when i took the first electronic course :

the circuit with three poles or more may oscillate at a certain frequency.

you can make a circuit that oscillates at 1Mhz. You should use an

op amp with Negative Feedback

and some capacitors and also resistors.

you can play with the values of the resistors and capacitance of the capacitors till you get the required frequency .

i will leave the rest for you my friend

hope you got something

#### Papabravo

Joined Feb 24, 2006
20,394
Originally posted by maniza_201@Mar 1 2006, 05:39 AM
how to design a circuit that can generate 1MHz signal?
[post=14486]Quoted post[/post]​
You can make a square wave relaxation oscilator with a CMOS Schmidt Trigger inverter such as a 74AHC1G14, one resistor, and one capacitor. Consult the data sheet to find the UTP and the LTP. These are the upper threshold point and the lower threshold point. Now use the equation for an RC charging discharging circuit to compute how long takes to charge the capacitor up to V=UTP with an initial condition of V=LTP, and discharge the capacitor down to V=LTP with an initial condition of V=UTP.

For a 1 MHz. oscilator you want to charge for 500 nanoseconds and discharge for 500 nanoseconds.

This will actually give you a value for the product of R and C. Then you pick a reasonable value of C, because you have many more choices for resistor values than capacitor values, and compute the value of R that you need.

If you want the frequency to be adjustable, then a potentiometer or a trimmer capacitor can be added to the circuit.

Hope this helps