LM-318, high frequency oscillator

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electronspeed

New Member

• Sep 5, 2009

• #1

Since BW of 741 opamp is 1MHz,,so RF cant be generated using it.I tried to generate 15MHz using LM-318 using the design principles of 741,,but didnt got the output.
please suggest,some measures.if design change plz tell me..

 

MikeMl

Well-Known Member

Most Helpful Member

• Sep 5, 2009

• #2

Look at the voltage gain of an **broken link removed**. No wonder you cant get any gain at 15MHz. You would have to use an OPAMP that has a GBW product of >100MHz to get any gain at 15MHz. Also at 15MHz, the parasitic capacitances due to layout and construction become critically important. You cant just breadboard it using a plug strip.

 

audioguru

Well-Known Member

Most Helpful Member

• Sep 5, 2009

• #3

The LM318 has a gain of only 1 (like a piece of wire) at 15MHz. Wien Bridge oscillators need the amplifier to have a gain of 3. A phase-shift oscillator needs the amplifier to have a gain of 29. A crystal oscillator needs a high gain amplifier. Which type of oscillator are you using? Why not use a newer opamp?

 

E

electronspeed

New Member

• Sep 5, 2009

• #4

thanx ,can you suggests some IC which can be employed for designing an oscillator(sine wave) in range (10-15) MHz..

 

audioguru

Well-Known Member

Most Helpful Member

• Sep 6, 2009

• #5

Sorry, your frequency is about 100 times higher than frequencies I usually work with.

 

RadioRon

Well-Known Member

• Sep 6, 2009

• #6

electronspeed said:

thanx ,can you suggests some IC which can be employed for designing an oscillator(sine wave) in range (10-15) MHz..

Click to expand...

Maybe something like this one:
https://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1022,P1858,D2967

Or why not use an application specific IC like this one:
https://www.electro-tech-online.com/custompdfs/2009/09/MAX2620.pdf

 

Last edited: Sep 6, 2009