Site Logo Home
 
rOm
Quest
Glossary
 
Random
Page
Search
Site
Lush
Sim
Class
Subject
Images
 
Help
FAQ
Sign
Up
Log
In
A Level     Audio     Power and RMS     >Pre-Amplifier<     Push-Pull     Tone Controls    

Audio Pre-Amplifier


Site for Eduqas/WJEC - Go to the AQA site.

  A Level    Audio  0 of 28    Question 1274    Audio Amplifiers 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set1 of 28    Question 1311    Audio Amplifiers 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set2 of 28    Question 653    Audio Power Amp 09 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set3 of 28    Question 654    Audio Power Amp 10 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set4 of 28    Question 655    Audio Power Amp 11 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set5 of 28    Question 656    Audio Power Amp 12 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set6 of 28    Question 657    Audio Power Amp 13 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set7 of 28    Question 658    Audio Power Amp 14 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set8 of 28    Question 660    Audio Power Amp 16 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set9 of 28    Question 661    Audio Power Amp 17 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set10 of 28    Question 662    Audio Power Amp 18 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set11 of 28    Question 663    Audio Power Amp 19 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set12 of 28    Question 664    Audio Power Amp 20 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set13 of 28    Question 665    Audio Power Amp 21 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set14 of 28    Question 918    Audio Power Amp 21 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set15 of 28    Question 666    Audio Power Amp 22 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set16 of 28    Question 667    Audio Power Amp 23 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set17 of 28    Question 944    Biasing 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set18 of 28    Question 355    Biasing 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set19 of 28    Question 945    Biasing and Signal Coupling 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set20 of 28    Question 881    Oscilloscope 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set21 of 28    Question 1273    Oscilloscope 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set22 of 28    Question 1289    Oscilloscope 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set23 of 28    Question 741    Push Pull Amplifier 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set24 of 28    Question 742    Push Pull Amplifier 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set25 of 28    Question 743    Push Pull Amplifier 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set26 of 28    Question 740    Push Pull Amplifier 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set27 of 28    Question 739    Push Pull Amplifier 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set28 of 28    Question 1440    Push Pull Amplifier 
Score 0/0 
Not attempted  
Last Answer  
Deadline not set  Questions 0 to 28   -->  View All  

Audio pre-amplifiers often have an input impedance of about 47kΩ designed to match most other audio devices. For top quality the amplifier frequency response should cover at least the range of human hearing from 20 to 20,000 Hz.

If you select an op-amp with a gain bandwidth product of 1 MHz, the gain has to be limited to 50 or less or the high frequency performance will not meet the specification.

50   x   20,000 Hz   =   1 MHz. 

To get a pre-amp with more gain than this, two pre-amplifier circuits could be used or a higher performance chip could be specified.

Op-amp preamplifiers might suffer from input noise adding a hiss to the output. The commonly used 741 chip is not especially good in this respect. Other lower noise op-amps are available. Low noise transistors could also be used instead of an op-amp.

A Possible Circuit

The 47K resistor reduces the almost infinite input resistance.
The gain is set to 48, just below the limit of 50.
The chip is a version of the 741 chip with a gain bandwidth product of 1 000 000.

Non Inverting Audio Pre-Amp

Capacitor Calculations

C1 with the 47K resistor forms a passive high pass filter. To ensure it passes frequencies as low as 20 Hz, the capacitor must be calculated for that break frequency. The output will drop to 0.707 of maximum at this frequency.

Xc   =   R   =   1 / ( 2 Pi F C )   =   47 000

C1   =   1 / ( 2 x Pi x 47 000 x 20 )   =   169 nF        The nearest commonly available capacitors are 220nF or 470nF.        Using 470nF, the break frequency is about 9 Hz giving a comfortable margin of error.

C2 can be the same assuming the next subsystem input also has a 47K input resistance.

 

Subject Name     Level     Topic Name     Question Heading     First Name Last Name Class ID     User ID    

fff
Home
<<<
ppw
Pg Up
<<
ppp
Up
<
|||

>|<
nnn
Down
>
nnw
Pg Down
>>
lll
End
>>>

Close
Escape
X

Q: qNum of last_q     Q ID: Question ID         Score: num correct/num attempts         Date Done    

 

Submit
Enter

 

Question Text

image url

 


Help Link

Add     Delete     Clone     Edit     Hardness

Help Text
Debug


 

 

 

Contact, Copyright, Cookies and Legalities: C Neil Bauers - reviseOmatic V4 - © 2016/17

Hosted at linode.com - London

 

Please report website problems to Neil