development: |
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fast or as low noise designed class-A MOS-FET-PA |

fast or as low noise designed MOS-FET-PA with 150 W rms in class AB operation |

low noise preamp |

tube-sound with triode in signal path |

To drive Power-MOS-FETs without current do not exploid the possibilities of a MOS-FET. Upper critical frequency and turn-on time will be affected by the manner the MOS-FETs are driven. High-frequency circuitry is asked. We have developed a circuit, which can drive the gate capacity of the FET with more current. The driver is a combination of base-collector coupling with bipolar transistors, a current-source, which can drive fast up to 1/4 Amps. Have a look at the gate-current-schema. The fast MOS-FET-PA has to be compensated a little bit more for square-puls-operation as shown and needs 10 Ohm gate resistances to avoid gate current swinging.

It is possible to design this PA for minimum noise high-end version.

Literature: Halbleiterschaltungstechnik - Tieze/Schenk, Analoge Schaltungen - Seifart, Elektronik - Müseler/Schneider, The Art of Electronics - Horowitz/Hill

specifications with gate-current driver: | specifications without gate-current driver: | high-end version: |
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class-A small signal bandwidth: 4 Hz - 25 MHz gain bandwidth: 6.98 MHz slew-rate: 770 V/us transient overshoot: 3 % input restisance: 43 kOhm output resistance: 302 uOhm gain: 11.4 dB ueq,n = 46.8 nV/SQR(Hz) -> -111.92 dB/22 kHz/13 W harmonic distortion: < 0.110 % / 13 W, < 0.033 % / 1 W Po = 13/16.4/23.7 W rms at 8/6/4 Ohm |
class-A small signal bandwidth: 4 Hz - 7.3 MHz gain bandwidth: 2.58 MHz slew-rate: 235 V/us transient overshoot: 39 % input resistance: 43 kOhm output resistance: 299 uOhm gain: 11.4 dB ueq,n = 46.8 nV/SQR(Hz) -> -111.92 dB/22 kHz/13 W harmonic distortion: < 0.120 % / 13 W, < 0.042 % / 1 W Po = 13/16.4/23.7 W rms at 8/6/4 Ohm |
class-A small signal bandwidth: 4 Hz - 4.5 MHz gain bandwidth: 1.03 MHz slew-rate: 66.2 V/us transient overshoot: 3 % input resistance: 47.8 kOhm output resistance: 299 uOhm gain: 11.56 dB ueq,n = 20.7 nV/SQR(Hz) -> -120.9 dB/22 kHz/13 W harmonic distortion: < 0.0089 % / 13 W, < 0.0171 % / 1 W Po = 13/16.4/23.7 W rms at 8/6/4 Ohm |

fast MOS-FET-PA | simple MOS-FET-PA |
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small signal gain: | small signal gain: |
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slew-rate at full power with a jump: | slew-rate at full power with a jump: |
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transient overshoot: | transient overshoot: |
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gate-current of both MOS-FETs at a full power jump: | gate-current at a full power jump: |
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slew-rate, transient overshoot and gate current of the MOS-FETs at 13 Wrms square-pulse-operation: | slew-rate, transient overshoot and gate current of the MOS-FETs at 13 Wrms square-pulse-operation: |
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output at 13 Wrms square-pulse-operation (compensated): | output at 13 Wrms square-pulse-operation: |
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__High-End-MOS-FET-PA with 150 W rms in class AB-operation__

MOS-FET-PA in 150 W-Class-AB with Gate-Current-Driver for optimal square-pulse-operation. The compensation is adjusted for an transient overshoot of 3 %. Here two different versions. The differences are the quietness current of the differential amplifier and the compensation.

specifications fast version: | specifications high end version: |
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Class-AB small signal bandwidth: 4 Hz - 4.2 MHz gain bandwidth: 3 MHz slew-rate: 600 V/us transient overshoot: 11 % input impedance: 48.1 kOhm output impedance: 287 uOhm gain: 18.06 dB ueq,n = 14.32 nV/SQR(Hz) -> -123 dB/22 kHz/150 W harmonic distortion: < 0.027 % / 150 W, 0.025 % / 1 W Pa = 211/141/105 W RMS at 4/6/8 Ohm |
Class-AB small signal bandwidth: 4 Hz - 1.1 MHz gain bandwidth: 500 kHz slew-rate: 188 V/us transient overshoot: 3 % input impedance: 48.1 kOhm output impedance: 560 uOhm gain: 18.06 dB ueq,n = 10.42 nV/SQR(Hz) -> -129 dB/22 kHz/150 W harmonic distortion: < 0.033 % / 150 W, 0.0067 % / 1 W Pa = 211/141/105 W RMS at 4/6/8 Ohm |

fast MOS-FET-PA | high-end MOS-FET-PA |
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small signal gain: | small signal gain: |
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slew-rate at full power with a jump: | slew-rate at full power with a jump: |
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slew-rate, transient overshoot and gate current of the MOS-FETs at 150 Wrms square-pulse-operation: | slew-rate, transient overshoot and gate current of the MOS-FETs at 150 Wrms square-pulse-operation: |
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slew-rate, transient overshoot and gate current of the MOS-FETs at 150 Wrms square-pulse-operation: | slew-rate, transient overshoot and gate current of the MOS-FETs at 150 Wrms square-pulse-operation: |
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output at 150 Wrms square-pulse-operation: | output at 150 Wrms square-pulse-operation: |
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Low noise Preamp with operational amplifiers OPA1612 and OPA134 from Texas Instruments. The adjustment range for treble, presence and bass are about +/- 15 dB. The necessary gain is in the first stage to reduce noise. The degenerative feedback was designed with low impedance because of noise.

specifications: |
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with OPA1612 u. OPA134, original Texas Instruments small signal bandwidth: 4 Hz - 7.5 MHz power bandwidth: 4 Hz - 564 kHz slew-rate: 15.48 V/us input resistance: 100 kOhm output resistance: 1140.68 Ohm gain: 12.74 dB at 43 kOhm load equivalente input noise voltage: 3.69 nV/SQR(Hz) --> -123.4 dB at 22 kHz bandwidth and 3.07 Veff output voltage. harmonic distortion: 0.0058 % |

Preamp: |
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small signal gain: |
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full output at 500 kHz: |
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slew-rate and swing: |
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harmonic distortion: |
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equivalent input noise voltage: |
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__typically tubesound with triode and non-linear transformer:__

Many music-lover sense the sound of natural sound and Hi-Fi-Solid-State-Amplifiers subjective "cold" and "boring". This device produces the "warm", "interesting" sound of tube amplifiers by a pentode as triode. The tube-sound results from the non-linear characteristik of the tube Ik=kx(Ust)^3/2 and of the non-linear transformer.

Input- and output voltage is in this design about 500 mVs. disturption adjustment with R6 (saturation degree 0 Ohm to 330 Ohm). With R1 (plate current 180 Ohm + 470 Ohm Poti) the anode alternate current can be adjusted. The very low-noise operational amplifier regulates the saturation degree of the tube. The THD of the 1 kHz-signal is at 2.1 mAss anode alternating current 2.33 %. with this saturation degree of the tube.

Note: A simulation with a wav-file in LTspice has shown that the result is good. [simulation output 1] [simulation output 2]

Thanks to Andreas Fecht and Alexander Bordodynov/Russia, who had some ideas for this.

specifications: |
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bandwidth: 30 Hz - ... Hz input resistance: 100 kOhm output resistance: 120 Ohm gain: 0 .. 6.02 dB an 47 kOhm Last >equivalente input noise voltage: 6.37 nV/SQR(Hz) --> -120.6 dB bei 22 kHz bandwidth and 1 Veff. harmonic distortion: 1.5 % .. 14.5 % |

circuit for 1 channel: |
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Grid 3 to Kathode |

small signal gain: |
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in- and output signal 1 kHz, moderate adjustment: |
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spectum of the disturbed signal: |
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