Transfer Funtion of the given circuit ?

sameerdhiman · 8th October 2011, 09:02 AM

Hi,

Please give me the transfer function of the following circuit. Where R1,R2,R3,R4 and R5 are not equal.

DF96 · 8th October 2011, 12:00 PM

How many marks will your teacher give me for the answer?

Ron E · 8th October 2011, 03:42 PM

Quote:

Originally Posted by sameerdhiman

Hi,

Please give me the transfer function of the following circuit. Where R1,R2,R3,R4 and R5 are not equal.

You should check out a neat little program called sapwin

SY · 8th October 2011, 04:20 PM

Just remember that the voltages at inverting and noninverting inputs are equal, that the current flowing into the inverting and noninverting inputs is zero, and it will be pretty easy to set up the basic equations to solve for Vo/Vi.

jcx · 8th October 2011, 08:57 PM

it actually "safer" to explicitly include op amp gain "A" and derive the equations

you can always take the limit as A goes to infinity later - but by assuming it from the start you may save a term or two in the calculations or you may have your solution "blow up" from the infinity you are implicitly carrying around

the op amp Howland current source is a favorite nasty problem set for those not understanding the "null injection" implicit infinity

dchisholm · 8th October 2011, 09:24 PM

What method do you think is best for solving this problem, and how far along did you get?

Dale

sameerdhiman · 10th October 2011, 03:48 PM

@DF96
I am not a student in any institute so do not expect any Marks.

@SY, jcx
Thank you, I solved it using superposition theory.

R1 and R2 forms voltage divider for Non-Inv voltage. R3||RD forms Rg and R4 forms Rf. So Non-Inv, Inv output voltage will be

Vninv = V1*[R2/(R1+R2)]*[1+{R4/(R3||RD)}]
Vinv = V1*-(R4/R3)

Vout = Vninv + Vinv

zigzagflux · 10th October 2011, 05:22 PM

Would you not want Vout in terms of V1 ?

DF96 · 10th October 2011, 05:49 PM

Quote:

Originally Posted by sameerdhiman

I am not a student in any institute so do not expect any Marks.

Good. Sorry for jumping to conclusions, but your question looked like homework.

I'm not certain that your result is correct. I would expect to see two simultaneous equations involving Vin and Vout, which you then invert to get Vout in terms of Vin. What is RD?

sameerdhiman · 10th October 2011, 07:17 PM

Sorry, R5=RD (In practical circuit R5 will be variable resistor e.g. JFET or LDR)

I've verified the equation with LTSpice.

If you any other equation/solution please post that.

8th October 2011, 04:20 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Just remember that the voltages at inverting and noninverting inputs are equal, that the current flowing into the inverting and noninverting inputs is zero, and it will be pretty easy to set up the basic equations to solve for Vo/Vi. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

10th October 2011, 03:48 PM	#7
sameerdhiman diyAudio Member Join Date: Nov 2009 Location: Ghaziabad (Delhi NCR)	@DF96 I am not a student in any institute so do not expect any Marks. @SY, jcx Thank you, I solved it using superposition theory. R1 and R2 forms voltage divider for Non-Inv voltage. R3\|\|RD forms Rg and R4 forms Rf. So Non-Inv, Inv output voltage will be Vninv = V1[R2/(R1+R2)][1+{R4/(R3\|\|RD)}] Vinv = V1*-(R4/R3) Vout = Vninv + Vinv __________________ Regards, Sameer Dhiman

10th October 2011, 07:17 PM	#10
sameerdhiman diyAudio Member Join Date: Nov 2009 Location: Ghaziabad (Delhi NCR)	Sorry, R5=RD (In practical circuit R5 will be variable resistor e.g. JFET or LDR) I've verified the equation with LTSpice. If you any other equation/solution please post that. __________________ Regards, Sameer Dhiman

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Getting transfer characteristics	oshifis	Tubes / Valves	1	12th August 2008 11:14 PM
Need transfer software for my Ipod!!!	michael9827	Instruments and Amps	3	14th June 2008 04:02 PM
transfer function	jenks	Solid State	31	24th April 2008 08:28 PM
Transfer Function	jclouse	Multi-Way	22	1st July 2006 01:19 PM
Transfer functions?	oracel	Multi-Way	15	23rd October 2004 01:34 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

8th October 2011, 12:00 PM	#2
DF96 diyAudio Member Join Date: May 2007	How many marks will your teacher give me for the answer?

8th October 2011, 08:57 PM	#5
jcx diyAudio Member Join Date: Feb 2003 Location: ..	it actually "safer" to explicitly include op amp gain "A" and derive the equations you can always take the limit as A goes to infinity later - but by assuming it from the start you may save a term or two in the calculations or you may have your solution "blow up" from the infinity you are implicitly carrying around the op amp Howland current source is a favorite nasty problem set for those not understanding the "null injection" implicit infinity

8th October 2011, 09:24 PM	#6
dchisholm diyAudio Member Join Date: Mar 2011 Location: St Louis, Mo	What method do you think is best for solving this problem, and how far along did you get? Dale

10th October 2011, 05:22 PM	#8
zigzagflux diyAudio Member Join Date: Oct 2006	Would you not want Vout in terms of V1 ?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read