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Subject: Re: HI FI amplifier question: help needed
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Sun, 08 Sep 2002 17:01:59 GMT
NNTP-Posting-Date: Sun, 08 Sep 2002 18:01:59 BST
Organization: Ireland On-Line Customer
The voltage into the load will depend on the clss of Amplifier in use. Since
the majority of amplifiers use some version of Class B,
The power supply to the Amplifier is the voltage difference between the 2
power supply pins hence if your power supply gives +16V and -16V with
respect to a ground, then your total voltage difference will be 32V.
assuming a Sinewave output signal - a pure tone. This is a symmetrical
supply. This will normally have a Peak value of say V - 2.0v ... In the
example above, A Positive peak value of +14V and a Negative peak value
of -14V or a Peak to Peak value of 28V. into the load.
The RMS Voltage from this example would be 0.707 times 14V
The RMS power delivered into the loudspeaker load would be (RMS Voltage) ^2
/ load resistance ( normally 8 ohm)
If the power supply is say 32V and Ground. ... This will be a single ended
supply. The Amplifier will have internal biassing circuits to ensure that
the steady voltage at the output of the transsitors is set at 16V Dc above
ground and that the voltage rises to 30V at the peak of the sine wave and
down to say 2V at the negative peak of the sine wave. A large series
capacitor would normally be used to protect the loadspeker from this
constant 16V DC .
The maximum voltage availalbe on the gate of the MOSFET is measured with
respect to its Source and can be got from a Datasheet for the device .
However the Max voltage is unlikely to exceed 20V.
"Guillaume sjm" wrote in message
> in an amplifier, there is a V amp followed by a Current Amp.
> The power supply is usually split in +V and -V
> I have a sudden doubt: Here is my question: the amplitude of the signal
> after the V amplification should be about the toal supply or half ? I mean
> if i supply with +-32Volts, the signal coming out of my Vamplifier should
> read +-16 volts or +-32 ?
> This is to make a hybrid with some tube Vamplification followed by Mosfet
> current amplification.
> Second question: a Mosfet can accept how much V on its Gate ? is it about
> the power supply or much less ? i noticed on some schematics that there is
> zener diode of about 15 Volts on the gate to protect it. In this case, is
> the Voutput limited to +-15Volts ?
> I must say I am a bit lost there...
> Thanks for your help
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