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Topic: 2N3055 transistor replacement (Read 1 time) previous topic - next topic


I am involve in an project that I need to hand it up to my school. It's an audio power amplifier,and recently I find a lot of knowledge about power amplifier and I decided to make an audio power amplifier basic on 2N3055 transistor.As the article"  how does 2n3055 work ": shows, 2N3055 transistor is a NPN power triode.the 2N3055 triode has three electrodes, a base pole (B), a collector (C) and a emitter (E). The triode is a current type control device. The current of the base to the emitter controls the current of the collector to the emitter, and the triode has three states, cut-off, amplification and saturation, and two PN knots inside the 2N3055 three pole, and the emitter junction (PN junction between the base and emitter). The collector junction (the PN junction between the collector and the emitter) is the cut-off of the emitter junction, the collector has no current on the collector, and the collector junction conduces to the complete conduction between the collector, and the current of the collector varies with the current of the emitter (the transistor can amplify the current, and the current on the collector is equal to the current of the emitter multiplier by the magnification. " The saturation is that the emission junction is fully conductive and the collector current is the largest.

This circuit is simple and the cost is low.The best power supply voltage is about 50V while it works from 30V to 60V .It biggest input voltage is about 0.8V to 1V.and the output power is about 60W.

The capacitance C1 regulates low frequency (bass), and as the capacitance increases, the low frequency becomes louder and louder.The capacitor C2 regulates a higher frequency (Gao Yin), and as the capacitance increases, it becomes louder and louder at higher frequencies.This is a class B amplifier, which means that the push-pull output transistor must be applied to a quiescent current, even without any input signal. The current can be regulated by a 500 Omega resistor setting.

However,I have a question: Can I use other NPN type power transistor instead of 2N3055? 
How about darlington type´╝č


Jun 21, 2018, 11:49 am Last Edit: Jun 21, 2018, 11:51 am by MarkT
The modern equivalent, _much_ better gain and speed, would be something like the NJW3281 and NJW1302
complementary pair.  Then you could use a fully complementary output section rather than the quasi-complementary one in that diagram.

The 2N3055 is 50 years old and a pretty poor performer - no self-respecting new design should be using it(!)

Yes you can use darlington output stage, you'll need a higher bias voltage and you'll get better current
handling with the right combination, but note that a discrete darlington from carefully selected components
is the way to go, 3281/1302 output devices being a good choice.

There are a lot of improvements that can be made to that circuit that will reduce the distortion significantly,
checkout the works of Douglas Self, Bob Cordell and others.  For instance the input stage isn't a differential
pair driving a current mirror, so its going to be pretty non-linear from the get-go.  Adding an output inductor
would be a wise precaution against oscillation into difficult loads too.

The capacitor C2 regulates a higher frequency (Gao Yin), and as the capacitance increases, it becomes louder and louder at higher frequencies
No, its function is to stop the amplifier oscillating, its a Miller compensation capacitor and it
has no effect on the gain in the audio band which is set by the feedback network.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


Its look like you find this circuit in museum, follow Mark advice.


Jun 21, 2018, 02:07 pm Last Edit: Jun 21, 2018, 02:11 pm by ted


If you're going to go class D, at least go for one that's properly filtered(*), and these days you can
do rather better than 0.1% distortion too.

(*) unless you want EMI issues!
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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