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Class D Switching Power Amplifiers and Power D/A conversion

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Old 4th March 2010, 03:18 PM   #111
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and more?... LM319 and HFE4070 OK...but there's more than that? Should I remove the C11 and C12 as well?
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Old 4th March 2010, 03:27 PM   #112
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thank's AP2, like this?
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Old 4th March 2010, 03:32 PM   #113
AP2 is online now AP2  Italy
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do not be sad.
now is ok but Vogor job on this schematic.
from my point of view, my post (power stage) may be a good starting point for
a good discrete amplifier (sure, not esoteric),but very good resolution for ..jazz.
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Old 4th March 2010, 03:37 PM   #114
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Thank's to VOGOR to it's his schematic
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Old 4th March 2010, 03:45 PM   #115
AP2 is online now AP2  Italy
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thank at IR..for precision
but this is not important.
if I find a bit of time, I add the circuit on my "Power-Stage" for change to "Self-oscillating", and protection.
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Old 5th March 2010, 06:04 AM   #116
vogor is offline vogor  Russian Federation
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To what level limit an entrance signal two diodes on an input? There is an assumption that they will not allow to receive a total power and too early begin restriction. I am going to connect the lamp preliminary cascade but it is not assured of value of sensitivity of the amplifier, a signal I take from an analogue exit of a sound card of the computer.
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Old 5th March 2010, 08:59 AM   #117
81bas is offline 81bas  Germany
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Originally Posted by vogor View Post
To what level limit an entrance signal two diodes on an input? There is an assumption that they will not allow to receive a total power and too early begin restriction. I am going to connect the lamp preliminary cascade but it is not assured of value of sensitivity of the amplifier, a signal I take from an analogue exit of a sound card of the computer.
They do limit differential voltage between + and - inputs of opamp to about +/-0.7 Volts. But under normal operation these diodes do not limit signal at all, because the input signal will be always compensated to near zero by negative feedback at opamp inputs.
These diodes would limit the input music signal if they would be placed before R2. But they are placed after R2 so they are used only to protect opamp inputs at amp startup and shutdown, when there is nothing connected to the amp input...

With 48K NFB resistor (R3+R18) and with 2.2K input resitor the amp amplifies signal about 20 times. With 1V input signal you will get about 20V output signal. So to get the full output power with +/-65V rails you need about 2Vrms input signal.

Last edited by 81bas; 5th March 2010 at 09:04 AM.
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Old 5th March 2010, 09:35 AM   #118
vogor is offline vogor  Russian Federation
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Quote:
Originally Posted by 81bas View Post
They do limit differential voltage between + and - inputs of opamp to about +/-0.7 Volts. But under normal operation these diodes do not limit signal at all, because the input signal will be always compensated to near zero by negative feedback at opamp inputs.
These diodes would limit the input music signal if they would be placed before R2. But they are placed after R2 so they are used only to protect opamp inputs at amp startup and shutdown, when there is nothing connected to the amp input...

With 48K NFB resistor (R3+R18) and with 2.2K input resitor the amp amplifies signal about 20 times. With 1V input signal you will get about 20V output signal. So to get the full output power with +/-65V rails you need about 2Vrms input signal.
I thank for an explanation, but it is possible more in detail why they will not limit an entrance signal above 0,7V if they stand after resistor R2, in what a difference?
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Old 5th March 2010, 09:50 AM   #119
81bas is offline 81bas  Germany
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I thank for an explanation, but it is possible more in detail why they will not limit an entrance signal above 0,7V if they stand after resistor R2, in what a difference?
I have written it already: because the input signal will be always compensated to near zero by negative feedback at opamp inputs.

If in some moment at the input of amp (before R2) there will be +1V, then at amp output (after L1) there will be about -10V. And using the Ohms Law it is possible to calculate, that between R2 and R3 there will be near zero voltage at opamp inputs...

Precisely to say, the input signal will be mainly compensated via NFB, and the ripple current will be compensated via C2 and C3, but it is simplier to understand it, assuming that input signal will be compensated alone via global NFB

Last edited by 81bas; 5th March 2010 at 10:00 AM.
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Old 5th March 2010, 10:33 AM   #120
vogor is offline vogor  Russian Federation
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Originally Posted by 81bas View Post
I have written it already: because the input signal will be always compensated to near zero by negative feedback at opamp inputs.

If in some moment at the input of amp (before R2) there will be +1V, then at amp output (after L1) there will be about -10V. And using the Ohms Law it is possible to calculate, that between R2 and R3 there will be near zero voltage at opamp inputs...

Precisely to say, the input signal will be mainly compensated via NFB, and the ripple current will be compensated via C2 and C3, but it is simplier to understand it, assuming that input signal will be compensated alone via global NFB
Somehow strange it turns out, if on an amplifier input will be 2V that at factor of strengthening K=20 - on an exit should be 40V but how it is possible if these limiting diodes do not allow be formed potential differences between inputs opamp more than 0,7V I can not to understand why they will not limit a signal.
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