rocky500 Posted October 22, 2013 Posted October 22, 2013 I have a Amp here and I was under the impression it was a mosfet amp for some reason. I thought I saw it somewhere online a while ago. Could anyone look at the specs below and tell me what it is? Dual-mono power amplifierThe circuital topology of the power amp consists of three stages with double symmetrical differential pair cascode-loaded with local feedback, cascode gain stage with local feedback and Vbe multiplier, output darlington with two pairs of output transistor per channel. It also has a global feedback loop and a overload protection circuit, which senses current and voltage as well, with dynamic response to transients. Even the start-up delay circuit is made with discrete components. Pic of the inside if it helps at all.
Zaphod Beeblebrox Posted October 22, 2013 Posted October 22, 2013 I have a Amp here and I was under the impression it was a mosfet amp for some reason. I thought I saw it somewhere online a while ago. Could anyone look at the specs below and tell me what it is? Dual-mono power amplifier The circuital topology of the power amp consists of three stages with double symmetrical differential pair cascode-loaded with local feedback, cascode gain stage with local feedback and Vbe multiplier, output darlington with two pairs of output transistor per channel. It also has a global feedback loop and a overload protection circuit, which senses current and voltage as well, with dynamic response to transients. Even the start-up delay circuit is made with discrete components. Pic of the inside if it helps at all. Since it uses output Darlingtons, then it must be a BJT amp. If you can post the part numbers of the output devices, I can clarify further.
rocky500 Posted October 22, 2013 Author Posted October 22, 2013 Thanks Zaphod, I will open it up later and have a look. The output devices are those 8 oval shaped silver parts or those 6 transistors between them?
Zaphod Beeblebrox Posted October 22, 2013 Posted October 22, 2013 Thanks Zaphod, I will open it up later and have a look. The output devices are those 8 oval shaped silver parts or those 6 transistors between them? The silvery things.
rocky500 Posted October 22, 2013 Author Posted October 22, 2013 (edited) The silvery things. The silver thingy's are mj15024g and mj15025g starting one side it goes 2x mj15024g then 2x mj15025g the 2x mj15024g then 2x mj15025g The smaller black ones are mje15030g/31g Edited October 22, 2013 by rocky500
Zaphod Beeblebrox Posted October 22, 2013 Posted October 22, 2013 The silver thingy's are mj15024g and mj15025g starting one side it goes 2x mj15024g then 2x mj15025g the 2x mj15024g then 2x mj15025g The smaller black ones are mje15030g/31g Definitely BJT amp. Not MOSFET. The output devices are not Darlington types. MJ15024/25 devices are very robust output devices. 1
rocky500 Posted October 23, 2013 Author Posted October 23, 2013 (edited) Thanks Big Z. A bit more reading on the net suggests a Sziklai Pair, Connection or Compound / Complementary Pair, a complementary version of the Darlington. I always assumed (wrongly) the big silvery things were mosfets. Edited October 23, 2013 by rocky500
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