I decided to highlight this scheme as a separate topic, because a concept has been formed both in terms of topology, element base, correction features, and, in fact, sound.

This scheme was called Fury (FURY).

circuit features:

1) the circuit of the voltage amplifier on JFET transistors in cascode inclusion

2) two NFB circuits, one of which covers the output capacitor, the second also corrects the stability (taken from the output of the amplifier)

3) complementary hexfet output

4) deep NFB (not less than 70dB)

5) inverting inclusion

The block diagram of Fury consists of three stages:

1st cascade on the field (jfet) with inverting inclusion

2-nd cascade of field devices (jfet) with dynamic load and low-impedance output for coordination with output stage

3rd cascade single follower with high-resistance input and with dynamic load + push-pull output stage on hexfettes in class AB

The nuances of the scheme:

* the first two stages without load have a gain of 95dB

* The contour of NFB at the input determines the overall gain of the circuit at 19.2 dB

* maximum input voltage (amplitude 3 volts)

* added RC input f = 816kHz to reduce dynamic distortion

* the second NFB circuit goes to the gate of the second stage, it is connected relative to the reference voltage of 13 volts (implemented on the zener diode), this circuit carries out correction of the amplifier at high frequencies for its stability and sets the operation mode of the output stage by constant voltage.

P.S. In the event of a break in any of the negative feedback loops or two at the same time, the circuit remains operational.

Nuances of the scheme of the 3rd cascade:

* at the input a field + bipolar transistor, which takes a signal from the source of a stable current source, because lower pre-amplifier output impedance is needed to match these stages

* dynamic load performed on mosfet IRF510

* The bias circuit of the output stage is made on the BD139 transistor with the IRF530 transistor - it provides smooth adjustment of the initial current of the output stage 100mA

* The thermosensitive element is the BD139 transistor, it is he who is screwed to the radiator.

* The use of IRF630 / 9630 turned out to be quite a musical complementary pair ...

Circuit Parameters:

* Ku = 19.2dB

* Uin max ~ 3V (amplitude), Uin nom ~ 2V (amplitude)

* P out (RMS) max = 40 watts (4 Ohms)

* slew rate SR = 5.84V / microS

* Frequency response in the frequency range 1-100000Hz is 0.05dB

* uneven phase response -1.5 degrees (20 kHz) and -7 degrees (100 kHz)

* delay at a frequency of 100 Hz - 0.24 microS, at a frequency of 20 Hz - 1.4 microS, at a frequency of 5 Hz - 96 microS

* output impedance R (i) 0.34 ohm ...

* the depth of the negative feedback in the frequency range 1-1000Hz is 76dB, at a frequency of 20kHz - 70dB

* THD distortion (nominal) at a frequency of 1 kHz less than 0.001% (0.0004%), at a frequency of 20 kHz - 0.006%

* initial current of the output stage 100mA

* power scheme - you can use unstabilized

This scheme was called Fury (FURY).

circuit features:

1) the circuit of the voltage amplifier on JFET transistors in cascode inclusion

2) two NFB circuits, one of which covers the output capacitor, the second also corrects the stability (taken from the output of the amplifier)

3) complementary hexfet output

4) deep NFB (not less than 70dB)

5) inverting inclusion

The block diagram of Fury consists of three stages:

1st cascade on the field (jfet) with inverting inclusion

2-nd cascade of field devices (jfet) with dynamic load and low-impedance output for coordination with output stage

3rd cascade single follower with high-resistance input and with dynamic load + push-pull output stage on hexfettes in class AB

The nuances of the scheme:

* the first two stages without load have a gain of 95dB

* The contour of NFB at the input determines the overall gain of the circuit at 19.2 dB

* maximum input voltage (amplitude 3 volts)

* added RC input f = 816kHz to reduce dynamic distortion

* the second NFB circuit goes to the gate of the second stage, it is connected relative to the reference voltage of 13 volts (implemented on the zener diode), this circuit carries out correction of the amplifier at high frequencies for its stability and sets the operation mode of the output stage by constant voltage.

P.S. In the event of a break in any of the negative feedback loops or two at the same time, the circuit remains operational.

Nuances of the scheme of the 3rd cascade:

* at the input a field + bipolar transistor, which takes a signal from the source of a stable current source, because lower pre-amplifier output impedance is needed to match these stages

* dynamic load performed on mosfet IRF510

* The bias circuit of the output stage is made on the BD139 transistor with the IRF530 transistor - it provides smooth adjustment of the initial current of the output stage 100mA

* The thermosensitive element is the BD139 transistor, it is he who is screwed to the radiator.

* The use of IRF630 / 9630 turned out to be quite a musical complementary pair ...

Circuit Parameters:

* Ku = 19.2dB

* Uin max ~ 3V (amplitude), Uin nom ~ 2V (amplitude)

* P out (RMS) max = 40 watts (4 Ohms)

* slew rate SR = 5.84V / microS

* Frequency response in the frequency range 1-100000Hz is 0.05dB

* uneven phase response -1.5 degrees (20 kHz) and -7 degrees (100 kHz)

* delay at a frequency of 100 Hz - 0.24 microS, at a frequency of 20 Hz - 1.4 microS, at a frequency of 5 Hz - 96 microS

* output impedance R (i) 0.34 ohm ...

* the depth of the negative feedback in the frequency range 1-1000Hz is 76dB, at a frequency of 20kHz - 70dB

* THD distortion (nominal) at a frequency of 1 kHz less than 0.001% (0.0004%), at a frequency of 20 kHz - 0.006%

* initial current of the output stage 100mA

* power scheme - you can use unstabilized

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