Audio power amplifier

An audio power amplifier comprising:

• a first-stage amplifier circuit for amplifying an audio frequency signal,
• a second-stage amplifier circuit including an n-p-n transistor and a p-n-p transistor, said transistors being connected in complementary symmetry form for phase inverting the output signal of said first-stage amplifier circuit, said second-stage amplifier circuit also serving as a drive stage, and a last-stage power amplifier circuit including a pair of p-channel and n-channel power field-effect transistors having drain voltage versus drain current characteristics similar to static plate voltage versus plate current characteristics of a triode vacuum tube and connected in complementary symmetry form for power amplifying output signals from said second-stage amplifier circuit,
• the output signal from said second-stage n-p-n transistor being connected to drive said p-channel power field-effect transistor having triode characteristics, the output signal from said p-n-p transistor being connected to drive said n-channel power field-effect transistor having triode characteristics.

An audio power amplifier comprising a first-stage amplifier circuit including an n-p-n transistor and p-n-p transistor, said transistors being connected in complementary symmetry form for amplifying an audio frequency signal, a second-stage amplifier circuit connected to the output side of said first-stage amplifier circuit including a second n-p-n transistor and a second p-n-p transistor, said second transistors being connected in complementary symmetry form, said second-stage amplifier circuit also serving as a drive stage, and a last-stage power amplifier circuit including a p-channel power field-effect transistor and a n-channel power field-effect transistor, said field-effect transistors having drain voltage versus drain current characteristics similar to static plate voltage versus plate current characteristics of a triode vacuum tube and being connected in complementary symmetry form for amplifying output signals of said second-stage amplifier circuit, the output signal from said second n-p-n transistor being connected to drive said p-channel power field-effect transistor, the output signal from said second p-n-p transistor being connected to drive said n-channel power field-effect transistor.