How can i make voltages?

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tomato

Joined: 31 Oct 2007
Posts: 16

01 Nov 2007 7:34 How can i make voltages?

Hi,all

I wanna make voltages to provide a regulated supply for core circuit

What can i use in A and B block?

help me !!

pouchito

Joined: 29 May 2006
Posts: 156
Helped: 22

01 Nov 2007 16:43 How can i make voltages?

not clear?
can you explain?
you mean you want to use a single power op amp ?
use LM358

Old Nick

Joined: 14 Sep 2007
Posts: 445
Helped: 49

01 Nov 2007 16:59 Re: How can i make voltages?

If you want to make the voltages off chip then obviously, you can just use voltage regs.

To create them on chip, you'll need to design such circuits yourself. A quick search on google should give you plenty of schematics, you'll just need to sim them to find out if the'll do what you need.

You'll need to have a very clear idea of the amount of current these will have to supply, and (obviously) design for that.

hr_rezaee

Joined: 06 Oct 2004
Posts: 892
Helped: 88
Location: Iran-Mashhad

01 Nov 2007 17:53 How can i make voltages?

Hi
If you want to design it as on chip part, use LDO.
regards

tomato

Joined: 31 Oct 2007
Posts: 16

02 Nov 2007 6:01 How can i make voltages?

I am sorry to confuse. I want to design on chip.
If i design as Fig A and B without external, is it OK?

Q1. If i use the Fig.B, what kind of type pass transistor of LDO is used as vss power?
I have to use nmos for sinking current?

hr_rezaee

Joined: 06 Oct 2004
Posts: 892
Helped: 88
Location: Iran-Mashhad

02 Nov 2007 8:17 How can i make voltages?

Hi
you must explain more.
regards

yaodao

Joined: 31 Oct 2001
Posts: 21

02 Nov 2007 8:19 Re: How can i make voltages?

maybe you should give some parameters just like input voltage,output voltage and output current,so could anyone help you.

tomato

Joined: 31 Oct 2007
Posts: 16

02 Nov 2007 8:31 How can i make voltages?

pls refer to the attached file..

Input vef. = 3.5V
Output vtg = 1V

loding current of output is about 100mA.

Sorry, but you need login in to view this attachment

tomato

Joined: 31 Oct 2007
Posts: 16

02 Nov 2007 9:45 How can i make voltages?

One more question about LDO..

Vref terminal of the Fig. A is on '-' , and B is not.
what's different?

thanks..

mists

Joined: 14 May 2002
Posts: 380
Helped: 33
Location: China

02 Nov 2007 9:51 How can i make voltages?

1 is right, 2 wrong, it is positive feedback

hr_rezaee

Joined: 06 Oct 2004
Posts: 892
Helped: 88
Location: Iran-Mashhad

02 Nov 2007 16:33 How can i make voltages?

Hi
yes, Fig A is true.
As I know you must buffer output.
(current can effects on thid circuit)
If you use buffer, it can sink and source current and there will be no problem.
regards

tomato

Joined: 31 Oct 2007
Posts: 16

05 Nov 2007 7:52 How can i make voltages?

thanks...all
I have one more question
For example,
Vout=Vref(1+R1/R2)
Vref=3.5 ,1.5V and Vout to make is 1V as shown in the 2nd circuit.
Vout is always over Vref. how to make?

and,
If i use the 2nd circuit, what kind of type pass transistor of LDO is used as vss power?
I have to use nmos pass tr. for sinking current?

thanks for your help!!

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tomato

Joined: 31 Oct 2007
Posts: 16

06 Nov 2007 3:36 Re: How can i make voltages?

hr_rezaee wrote:

Hi
yes, Fig A is true.
As I know you must buffer output.
(current can effects on thid circuit)
If you use buffer, it can sink and source current and there will be no problem.
regards

thanks..jr_rezaee

can u explain about the buffer output? or give me a related paper?