BJT are not able to increase voltage because
hFE is less when tension is more
so BJT AMP make a compression of signal
for that reason
Voltage Amplification Stage is a toroidal transformer
and the gain of BJT AMP is 3dB 😛😛😛
Note:
1. W2 - omitted (In case of many users have not enough skill and equipments to adjust the offset of amplifier - half value. Then omitted the W2 to make it simple).
2. R28 = 220 ohm in case of omitted W2 (viceversa shorth)
Adjustment:
1. Apply power but do not install power output transistors in this moment, adjust W1 to make 1K (FET source resistor) to 2.3---2.6VDC
2. Adjust W3 to set the voltage difference between pin 1 & 3 of power output transistor to 0.45V or less. Do not install power output transistor in this moment too!
3. Test the DC offset with W2. Install the power output transistors: the output DC offset is 25mV or less. Otherwise adjust W2🙂
Adjust W3 and check the voltage drop of 0.22 ohm / 5W resistor. 10mV to 40mV (depends on effiency of the heatsinks) is ideal volatge drop.
hFE is less when tension is more
so BJT AMP make a compression of signal
for that reason
Voltage Amplification Stage is a toroidal transformer
and the gain of BJT AMP is 3dB 😛😛😛
Note:
1. W2 - omitted (In case of many users have not enough skill and equipments to adjust the offset of amplifier - half value. Then omitted the W2 to make it simple).
2. R28 = 220 ohm in case of omitted W2 (viceversa shorth)
Adjustment:
1. Apply power but do not install power output transistors in this moment, adjust W1 to make 1K (FET source resistor) to 2.3---2.6VDC
2. Adjust W3 to set the voltage difference between pin 1 & 3 of power output transistor to 0.45V or less. Do not install power output transistor in this moment too!
3. Test the DC offset with W2. Install the power output transistors: the output DC offset is 25mV or less. Otherwise adjust W2🙂
Adjust W3 and check the voltage drop of 0.22 ohm / 5W resistor. 10mV to 40mV (depends on effiency of the heatsinks) is ideal volatge drop.
Attachments
Maybe you are inventing a new Electronics here 😉
What shall we do with the billion billion BJT voltage amps out there?
If the design is based on voltage constraints and current gain, you may have problems.
Best not to design around variable variables like Hfe, Vbe or Vceo. You may have to pick and choose and will never find a replacement transistor that works without circuit modifications.🙂
Best not to design around variable variables like Hfe, Vbe or Vceo. You may have to pick and choose and will never find a replacement transistor that works without circuit modifications.🙂
Not to forget that Hfe(Beta) varies *very* little (if anything at all) with Vce, while it varies *a lot* with collector current.
As a side note I very much doubt that the expensive, complex and heavy solution posted above is as linear as a humble (20 cents) 1/2 TL072, set for 20X gain.
As a side note I very much doubt that the expensive, complex and heavy solution posted above is as linear as a humble (20 cents) 1/2 TL072, set for 20X gain.
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