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Npn emitter follower question

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anney2n

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I am setting up a npn in emitter follower as a switch between two ic's. The ic pin is the load. Do I need to reference the emitter to ground, as the ic is referenced to ground?
 

What do you mean "referenced to ground"? Are you expecting the ic input to provide the proper emmiter load without a resistor? And why are you using an emitter follower as a switch?
 

I can't post pics as I am away from my computer so I will try to explain: resistor between emitter and input, but do I need a resistor between emitter and ground?
 

Also, I don't need or want a large current gain.
 

Hi,

Your informations are totally confusing.
a npn in emitter follower as a switch
An emitter follower is a circuit for analog signals. Voltage gain about +1, current gain maybe 100.
--> Not suitable as a switch

The ic pin is the load.
An IC input usually is no suitable load for an emitter follower. It makes signals slow.

Do I need to reference the emitter to ground, as the ic is referenced to ground?
The whole circuit needs to be referenced to GND: IC1, IC2 and the circuit inbetween.
But don't connect the emitter directely to GND...impossible for an emitter follower.

You still didn't answer htis question:
And why are you using an emitter follower as a switch?

: resistor between emitter and input,
This makes no sense.

do I need a resistor between emitter and ground?
This is the usual emitter follower connection.

Also, I don't need or want a large current gain.
But this is the intention of an emitter follower...so what's your idea.

Before designing a circuit..there is a functional requirement..and electrical specifications.
Both are completely missing in your posts.
Without them it is impossible to say if a circuit is suitable or not.

Klaus
 

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