low voltage comparison/amplification

[nges]

hello guys; i am new to this forum:

how can i amplify a voltage of about 0.3v

also; if i am to use a comparator to compare between 0v and 0.3v and send out Vcc or 0v depending on which one was greater; which OP AMP can i possibly use;

 

[nges]

controlling small voltages with pic16f887

hello everyone;

Is it possible for me to use a voltage of about 0.3v to have a 5v at the output?:
confused:

 

[shumifan50]

See this thread:
HERE

 

[(*steve*)]

Sure, the PIC can use an analog input to detect a voltage of 0.3V above ground. From there you can do whatever you want, changing an output pin from low to high is one of them.

 

[(*steve*)]

nges, clearly this is one question. Asking it twice in two different threads in two different sections with two different topics is REALLY annoying.

 

[shrinivasdevkar]

you can use comparator ic LM324 which is quard comparator

 

[KrisBlueNZ]

LM324 is a quad op-amp. It can be used as a comparator though. LM339 is a quad comparator.

 

[shrinivasdevkar]

thnks sir to correct me....

 

[shrinivasdevkar]

sir in case of LM324 if we not applying input, only ref. voltage is applied then how it gives logic high at its output pin (e.g. pin no.1 =3.5-4volt)

 

[KrisBlueNZ]

I'm not sure what you're asking.

If you connect a reference voltage to one input, but leave the other input floating, the output state is undefined. It could be high or low or somewhere in between, and it could oscillate. You need to connect both inputs to something.

If the non-inverting ("+") input voltage is higher than the inverting ("-") input voltage, the output will go high. It will not pull all the way up to the positive power supply because of how the output stage is designed, with an emitter follower at the top. (Look at the equivalent schematic diagram in a data sheet.)

 

[shrinivasdevkar]

LM324

Sir i will check that connection. But another problem is that i 'm taking input from another device display and 5V supply and referance voltage is from anather separate power supply . How the connection is to be done. We have to make both ckt GND. short or not. I'm tried in that way but Voltage is falls down from 5V to 0.6V like that...???

 

[KrisBlueNZ]

Yes, you would normally connect the 0V rail of one circuit to the 0V rail of the other circuit.

Try just connecting the 0V rails together. If this causes a problem, the two circuits were not completely isolated from each other, so you need to fix that. If the problem only shows up when you connect the +5V power rail from one circuit to the other, there's probably a power supply short on the second circuit, or perhaps you're connecting it with the wrong polarity.

You're asking a lot of vague questions. It's really difficult for us to know how to answer when you don't give any background information. You sound like a beginner, and there are so many mistakes that you might have made that it's hard to know what to suggest first.

You need to start by describing the whole project, any special components that are used (e.g. ICs, modules) (with full part numbers, and preferably, links to data sheets), then post complete schematics.

Also, this discussion is not related to the first part of the thread. You have hijacked someone else's thread. I (or another moderator) will move this discussion to a new thread once we have enough information to decide what the name of the thread should be.

 

[nges]

thks for ur answers
posting it twice was because i had some problems with my connection