IET
Decrease font size
Increase font size
Topic Title: Do I need a Load Resistor?
Topic Summary: I have a detector feeding into an amplifier circuit and need to know if I should use a load resistor?
Created On: 12 July 2012 03:50 PM
Status: Read Only
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 12 July 2012 03:50 PM
User is offline View Users Profile Print this message



safortune

Posts: 8
Joined: 27 October 2010

Hi all,

I don't fully understand the purpose of load resistors and could do with some advice...

I have a detector (which contains and amplifier) which has an output load resistance of 50KOhm. This feeds into a potential divider of R1 = 1M and R2 = 33K, and then into a series of op amps.

Do I need to include a 47KOhm load resistor (connected to ground) before the potential divider? If so, why?

Thanks for your help.

SF
 12 July 2012 04:25 PM
User is offline View Users Profile Print this message



ANFierman

Posts: 136
Joined: 25 July 2008

" ...a detector (which contains and amplifier) which has an output load resistance of 50KOhm."

From what you say it is not clear of your amplifier has a 50k output resistance or requires a minimum load resistance of 50k in order to operate correctly.

Can you point us to a datasheet for it?

In the meanwhile you might like to have a play with a simple model of the former possibility here:

https://www.circuitlab.com/circuit/29gq27/sensor-amp-01/



-------------------------
Andy Fierman

---------------------------
http://signality.co.uk
---------------------------
 20 November 2012 02:55 PM
User is offline View Users Profile Print this message



Claudfox

Posts: 3
Joined: 09 November 2012

What could be the case is that your amplifier needs a minimum load resistance of 50kOhm. in that case you would need to include the load resistor.

Edited: 20 November 2012 at 03:04 PM by Claudfox
 16 April 2013 11:54 PM
User is offline View Users Profile Print this message



kengreen

Posts: 400
Joined: 15 April 2013

You have not supplied the necessary info:?
(a) Are you working with semiconductors or valves?
(b) Does the input to your following amplifier require a voltage feed or a current feed?

(c) the total effective value of the load resistor determines the bandwidth of the driving tuned circuit

d) are you aware that, in a current circuit, a potential divider must be replaced by a current-divider? This is why the volume controls of most "trannies" do not work properly. Feed-in at the tapping
point and out across the entire divider. I kid you not.

ken Green
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.