IF amplifier transformers are simply tunable inductors, usually with an integral fixed capacitor, and are typically used inside cheaper transistor radios.

WWW.ELECTRONICS-TUTORIALS.COM


Please visit VK2TIP's Book Shelf. My personal recommendations, thanks.

LAST MODIFIED:
Sunday, 23-Jun-2013 12:55:31 PDT

IF AMPLIFIER TRANSFORMERS


 

Authored by Ian C. Purdie VK2TIP

Find us on Google+

 

Share

     

What are IF amplifier filters?

IF amplifier transformers are simply tunable inductors, usually with an integral fixed capacitor, and are typically used inside cheaper transistor radios.

Mostly they are used as "synchronously tuned filters" because each stage is coupled by an active device.



This image is copyright © by Ian C. Purdie VK2TIP - if amplifier filter block diagram

Figure 1 - if amplifier filter block diagram

Now in the if amplifier filter block diagram schematic above here I've depicted three I.F. transformers separated by two stages of amplification which could be valves, transistors or integrated circuits. We will not consider the actual active or amplifier stages here, just the I.F. transformers. Another tutorial dealt with the details the IF amplifier filtering block itself.

Here we will confine ourselves to the I.F. transformers (or IF transformers) themselves. The information I have provided here may be regarded as merely being "typical" of what you might encounter inside a transistor radio. That means don't take it for granted that this "IS" the case.  O.K.?

The data presented below deals with the Mouser transformers only. There are numerous other manufacturers including Toko and many others. The variety of similar looking, but indeed quite different, IF transformers is astonishing. The table covers 455 Khz IF transformers, 10.7 Mhz IF transformers and standard AM Radio band oscillator coils which are tuned by the 60 pF section of a 60 / 160 pF "plastic" variable capacitor.

If you ever see a complete Coilcraft or a J.W. Miller catalogue it is truly bewildering.



This image is copyright © by Ian C. Purdie VK2TIP - if amplifier transformer schematics

Figure 2 - if amplifier transformer schematics

Of course if your even only half awake you would realise the only difference between type 1 and type 2 is that the latter doesn't have the integral capacitor built in. Now look at this table. Just look at the variances in the "yellow" types alone.

Here is a table of typical IF amplifier transformers and oscillator coils

  455 Khz transformers
Mouser Number
Impedance
Application
Slug Colour
Schematic
Turns Ratio
Nominal
Inductance
Turns
[1 - 2]
Turns
[2 - 3]
Turns
[4 - 6]
42IF101
60K : 600
1st I.F.
Yellow
Type 1
22 : 1
680 uH
70
87
7
42IF301
50K : 500
1st I.F
Yellow
Type 1
20 : 1
680 uH
77
66
7
42IF102
30K : 500
2nd I.F
White
Type 1
22 : 1
680 uH
98
57
7
42IF302
30K : 500
2nd I.F
White
Type 1
22 : 1
680 uH
95
48
7
42IF103
20K : 6K
3rd I.F
Black
Type 1
6 : 1
680 uH
103
50
27
42IF303
20K : 5K
3rd I.F
Black
Type 1
7 : 1
680 uH
 102
41
21
 
  796 Khz (nominal) transformers
Mouser Number
Impedance
Application
Slug Colour
Schematic
Turns Ratio
Nominal
Inductance
Turns
[1 - 2]
Turns
[2 - 3]
Turns
[4 - 6]
 42IF300
AM Osc.
Tuning
Red
Type 2
10 : 1
360 uH
92
3
9
42IF100
AM Osc.
Tuning
Red
Type 2
13 : 1
360 uH
104
3
8
42IF110
AM Osc.
Tuning
Red
Type 2
35 : 1
360 uH
82
74
7
 
  10.7 Mhz transformers
Mouser Number
Impedance
Application
Slug Colour
Schematic
Turns Ratio
Nominal
Inductance
Turns
[1 - 2]
Turns
[2 - 3]
Turns
[4 - 6]
42IF122
15K : 300
2nd / 3rd IF
Brown
Type 1
14 : 1
4.5 uH
7
7
1
42IF129
15K : 100
2nd / 3rd IF
Black
Type 1
18 : 1
4.5 uH
5
9
2
42IF123
25K : 4K
1st IF
Green
Type 1
7 : 1
4.5 uH
12
6
1
 
  Variable frequency [no integral capacitor]
Mouser Number
Impedance
Application
Slug Colour
Schematic
Turns Ratio
Nominal
Inductance
Turns
[1 - 2]
Turns
[1 - 2]
Turns
[1 - 2]
42IF104
50K : 500
1st IF
Yellow
Type 2
22 : 1
680 uH
82
74
7
42IF106
20K : 5K
3rd IF
Black
Type 2
6 : 1
680 uH
103
50
27
42IF124
15K : 300
2nd / 3rd IF
Orange
Type 2
14 : 1
4.3 uH
7
7
1

A typical Mouser spec sheet can be had here. Spec Sheet for a 42IF124

Examining a typical IF amplifier transformer

We will consider the first one from our table above 42IF101. Here I've left the 180 pF capacitor out of the IF amplifier transformer schematic simply for clarity, it is normally connected internally across pins 1 and 3.



This image is copyright © by Ian C. Purdie VK2TIP - 1st IF amplifier transformer schematic

Figure 3 - 1st IF amplifier transformer schematic

A typical practical application can be seen in the tutorial on AM Radio receivers.

 

Custom Search

 


 

Got a question on this topic?

If you are involved in electronics then consider joining our "electronics Questions and Answers" news group to ask your question there as well as sharing your thorny questions and answers. Help out your colleagues!.

The absolute fastest way to get your question answered and yes, I DO read most posts.

This is a mutual help group with a very professional air about it. I've learn't things. It is an excellent learning resource for lurkers as well as active contributors.

RELATED TOPICS ON IF AMPLIFIER FILTERS

if amplifier filters

AM Radio receivers

band pass filters

high pass filters

low pass filters

active band pass filters

join our "electronics discussion group"

Link to this page

NEW! - How to link directly to this page

Want to create a page link to me from your site? It couldn't be easier. No HTML knowledge required; even the technophobes can do it. All you need to do is copy and paste, the following code. All links are greatly appreciated; I sincerely thank you for your support.

Copy and paste the following code for a text link:

<a href="http://www.electronics-tutorials.com/filters/if-amplifier-transformers.htm" target="_top">visit Ian Purdie VK2TIP's "IF Amplifier Transformers" Page</a>

and it should appear like this:
visit Ian Purdie VK2TIP's "IF Amplifier Transformers" Page

 


 
 
Click image to print out a printer friendly version of this page. print

Looking for more? Visit my site map page:

This site is hosted at WebWizards.Net for better value.


the author Ian C. Purdie, VK2TIP of www.electronics-tutorials.com asserts the moral right to be identified as the author of this web site and all contents herein. Copyright © 2000, all rights reserved. See copying and links. These electronic tutorials are provided for individual private use and the author assumes no liability whatsoever for the application, use, misuse, of any of these projects or electronics tutorials that may result in the direct or indirect damage or loss that comes from these projects or tutorials. All materials are provided for free private and public use.
Commercial use prohibited without prior written permission from www.electronics-tutorials.com.


Copyright © 2000, all rights reserved. URL - http://www.electronics-tutorials.com/filters/if-amplifier-transformers.htm

Updated 20th October, 2001

Contact VK2TIP