oscillator

Do you need the extra functions that a 555 has? If you just need a square wave can you use a crystal oscillator?

Of course, if you don't need it to be variable, a canned oscillator would do nicely.

No just a square wave. Do crytals offer just as good square wave ?

Ken

Not that stable. Actually I wanted to swap that with my 555 chip (with minor changes too) and the output will go to my base of my 2n3055 transistor. At first I was looking the 7555, but that seems to be too much on the border line I dont really want to go digital too like a vibrator.

ken

Ken O wrote: (snip)

So, are you saying you want to switch a 2N3055 on and off up to 20 million times a second?

well the 2n3055 is only good for 3 MHz, I'll have to chosse another chip that does faster. even that , it IS better the 555.

Ken

I think the 2N3055 has a current gain bandwidth product of between 2.5 and 3 MHz. That means that it has a current gain of only 1 at 3 MHz. Are you planning to drive the base with the same current you hope to switch through the collector? You also cannot produce a 3 MHz square wave output that way, because the harmonics of a 3 MHz square wave are

oscilators for higher frequencies are often built using schmitt inverters at these frequencies it's common to use a resonator or crystal to determine the frequecy rather than using a combination of resistor and capacitor.

Yes, do back up a few steps here. What solution or effect are you trying to rig up here, that needs a high(er)-current 20Mhz square wave?

Regards, ws

square

Better. Run one at 40Mhz and divide by two to get a perfect 20MHz.

Sorry for delay in replying