For not so disgusting. (APEX A40) 
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It has not been completed.For not so disgusting. (APEX A40)![]()
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Comparison of APEX-A40 and improved version.
APEX-A40 is an example of bad electronics.
Not necessarily bad, but there are many wrong part selection inside.
Sajti
To use MJE340 / 350 for such small currents talk about the extraordinary incompetence of the author of the APEX A40.
Especially T25 / 26 which need not be high voltage.
Sure. Another wrong decision is to use BC547/557 in the current mirror, because of the quasi saturation. BC337/327 is much better. BC550/560 would be better in the input stage because of the low Vce.
Another problem is the 2x1N4148 in the VAS, which gives not enough voltage shift. Much better to use LED instead of the 2 diodes.
Sajti
Comparison of the growth rate.
There is also a test with reduced C1 (10pF) to remove the influence of the R2C1 circuit.
APEX A40 (+87V/uS -53v/uS)
Sandy C1 = 100pF (+534V/uS -400v/uS)
Sandy C1 = 10pF (+829V/uS -920v/uS)
There is also a test with reduced C1 (10pF) to remove the influence of the R2C1 circuit.
APEX A40 (+87V/uS -53v/uS)
Sandy C1 = 100pF (+534V/uS -400v/uS)
Sandy C1 = 10pF (+829V/uS -920v/uS)
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Be used to Ic 1-2mA transistor with a maximum current 0,8A is a very bad idea.
Ft transistor for such small current is considerably less when the transistor is made for large Ic
But using BC547 as T17, and T18 is even worse. That transistors are close to the saturation, and BC547 is one of the worst candidate. Check this topic:Looking for a small signal NPN with no Quasi Saturation: MEASURED DATA
Sajti
So usually use a current mirror rather than current amplifier x5 and I secured Uce 4V of T15But using BC547 as T17, and T18 is even worse. That transistors are close to the saturation, and BC547 is one of the worst candidate. Check this topic:Looking for a small signal NPN with no Quasi Saturation: MEASURED DATA
Sajti
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So usually use a current mirror rather than current amplifier x5 and I secured Uce 4V of T15
Your solution is better in this case.
Sajti
Here gain without feedback.
And remove protection to understand easily scheme.
The use of T25/26 and T21 special tethering Т21/24 compensating h22b and Ccb of T16/17 allows to obtain amplification of 160db without the need for amplification in the T13/15 T14/18
And remove protection to understand easily scheme.
The use of T25/26 and T21 special tethering Т21/24 compensating h22b and Ccb of T16/17 allows to obtain amplification of 160db without the need for amplification in the T13/15 T14/18
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- Apex A40 fundamental improvement. (Sandy)