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GE863-QUAD
1vv0300715 Rev. 1 - 19/09/06
freq. = | 1 | = | 1 | [Hz] |
2π * R719*C726 | 2π * R711*C727 |
The buffer bandwidth at -3dB shall be 4KHz.
Note that the biasing of the operational amplifier is given for the inverting amplifier by the series divider
TIP: example of calculation.
Llet's assume you have a microphone with a sensitivity of
As reported at page XX , the electrical level output from the microphone will be :
MicLevel = (
but we have to consider 20dB loss due to the higher distance from the mouth of the talker ( 50cm ) .
MicLevel = ( -49.7) + (-20) = -69.7 dBVrms
corresponding to
MicVoltage = 10 (
In order to have a signal of 1 mVrms at the “Mic_HF” inputs , as suggested at TIP “environment consideration “,
the buffer must have a gain
GA= “Mic_HF /MicVoltage = (1*10
or +10 dB
Keeping in mind that “ balancing the line will double the signal”, to calculate the resistor values assign half of required gain GA to each amplifier section . And therefore GS =1,5times (or +3,52dB) .
Choosing as 10kΩ as the input resistance , the corresponding values for the resistors on the buffer will be :
R711 = GS * R708= 1.5*10 =15 kΩ
R719 = (GS
The commercial values of 15kΩ and 5.6kΩ be accepted .
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