Calculating transistor size

[zoorahk]

Hello:
I have been working on a paired transistor PNP, NPN amp for a primary square wave signal. I have looked at the specifications in the data sheets but it does not make since to me. I am assuming that there is a minimum volt, amp or watt threshold for every transistor before it starts operating. I would call it a "trip threshold" but I can't make heads or tails of the terminology. Can you tell me what spec in the data sheets refers to the point at which a transistor starts doing it's job? Or is there a formula I need to calculate what I need to know?

Thank you,
Zoorahk

 

[dkace]

Re: Transistor Sizing

If I understand correctly, you are using descrete NMOS and PMOS to build up an OPAMP.There should be characteristics like saturation, Nonsaturation, inversion etc. There is nothing like it? Can you upload a page of the datasheet or put the code of the device in order to look it up?

D.

 

[srieda]

Re: Transistor Sizing

If you mean Vk (cut-in voltage or the knee voltage), then it must be specified in the datasheet. If you are not talking about discrete devices, then lookup on the spice models in the library.
Hope this helps..