Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Voltage gain in power amplifier

Status
Not open for further replies.

praveen450

Member level 5
Joined
May 13, 2011
Messages
89
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,957
Hi,

What should be the minimum voltage gain in a class C power amplifier.Is it ok if the voltage gain is less than 0.5 in PA and still hyave the efficiency greater than 70%:?:
 

SkyHigh

Advanced Member level 1
Joined
Jan 13, 2005
Messages
432
Helped
79
Reputation
158
Reaction score
27
Trophy points
1,308
Activity points
7,319
Classification of amplifier is determined by efficiency. That's all.
Your voltage gain at 0.5 less than unity isn't important.
 

mtwieg

Advanced Member level 5
Joined
Jan 20, 2011
Messages
3,537
Helped
1,254
Reputation
2,514
Reaction score
1,233
Trophy points
1,393
Activity points
26,506
Well more specifically you want your power added efficiency... which will be low if your signal gain is poor.
 

chuckey

Advanced Member level 5
Joined
Dec 26, 2010
Messages
4,863
Helped
1,308
Reputation
2,622
Reaction score
1,283
Trophy points
1,393
Location
Southampton and holiday cottage in Wensleydale (UK
Activity points
31,695
PA = Powe Amplifier. It turns a voltage swing across a high impedance ( Pin = V^2/R) into a voltage swing across a lower impedance. It was a good term to use in the days of the thermionic valve where Pin was miniscule (very high input impedance) and Pout was perhaps 1000 times greater. With the advent of the junction transistor, with low input imedances, hence significent input power, the overall power gain could easily be as low as 3. MOSFETs with their high imput impedance, have got back to being more like a valve. PA is the term really for the output stage of a HiFi set or a transmitter rather then used for signal manipulation.
Frank
 

SkyHigh

Advanced Member level 1
Joined
Jan 13, 2005
Messages
432
Helped
79
Reputation
158
Reaction score
27
Trophy points
1,308
Activity points
7,319
True indeed...
In fact today, audio is going either Class A, AB or Class D.
Class C is just a classroom topic.

For power, Class D is current trend.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
48,165
Helped
14,195
Reputation
28,649
Reaction score
12,886
Trophy points
1,393
Location
Bochum, Germany
Activity points
279,088
Although it's not explicitely said in the initial post, I would expect that the question refers to RF PA (the only domain of class C according to my knowledge). If so, the operation frequency, transistor type (MOS or BJT) and circuit topology should be known for a specific answer.

It's obvious however, that a low power gain (e.g. < 15-20 dB) won't be compatible with high overall efficiency.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top