Current feedback audio power amplifier
First Claim
Patent Images
1. A power amplifier for electrical signal in the audio frequency range, comprising:
- an input stage including an audio frequency operational buffer amplifier having a pair of current supply ports, and an output connected in a local voltage gain feedback circuit, one input of said operational amplifier being connected to receive an electrical input signal in the audio frequency range and its other input connected in said voltage gain feedback circuit,an output terminal,a pair of current mirrors connected to supply transient currents to respective operational amplifier current supply ports in response to changes in said input electrical signal, and to provide mirrored values of said transient currents,a charge storage means connected to receive said mirrored currents and to adjust the voltage at said output terminal in response thereto,an output current gain stage connected in circuit between said signal storage means and said output terminal, anda current feedback circuit between said output terminal and said operational amplifier to assist voltage tracking between said output terminal and said electrical input signal.
2 Assignments
0 Petitions
Accused Products
Abstract
An audio power amplifier achieves a closed-loop bandwidth which is relatively independent of gain, and a very high slew rate capability, with a current feedback operational amplifier design. A separate operational amplifier which is connected as an integrator and operates at sub-audio frequencies compensates for the output terminal bias current of the first operational amplifier, thus mitigating the effects of current mirror mismatch in the current feedback circuit and allowing the overall output offset voltage to be significantly reduced.
14 Citations
23 Claims
-
1. A power amplifier for electrical signal in the audio frequency range, comprising:
-
an input stage including an audio frequency operational buffer amplifier having a pair of current supply ports, and an output connected in a local voltage gain feedback circuit, one input of said operational amplifier being connected to receive an electrical input signal in the audio frequency range and its other input connected in said voltage gain feedback circuit, an output terminal, a pair of current mirrors connected to supply transient currents to respective operational amplifier current supply ports in response to changes in said input electrical signal, and to provide mirrored values of said transient currents, a charge storage means connected to receive said mirrored currents and to adjust the voltage at said output terminal in response thereto, an output current gain stage connected in circuit between said signal storage means and said output terminal, and a current feedback circuit between said output terminal and said operational amplifier to assist voltage tracking between said output terminal and said electrical input signal.
-
-
2. A power amplifier for electrical signals in the audio frequency range, comprising:
-
an input stage including an audio frequency operational buffer amplifier having a pair of current supply ports, and connected in a voltage gain feedback circuit, one input of said operational amplifier being connected to receive an electrical input signal in the audio frequency range and its other input connected in said voltage gain feedback circuit, an output terminal, a pair of current mirrors connected to supply transient currents to respective operational amplifier current supply ports in response to changes in said input electrical signal, and to provide mirrored values of said transient currents, a change storage means connected to receive said mirrored currents and to adjust the voltage at said output terminal in response thereto, an output current gain stage connected in circuit between said signal storage means and said output terminal, a current feedback circuit between said output terminal and said operational amplifier to assist voltage tracking between said output terminal and said electrical input signal, and a sub-audio frequency operational amplifier connected in a voltage gain feedback circuit with a sub-audio crossover frequency, one input of said sub-audio frequency operational amplifier being connected to receive sub-audio frequency components of said electrical input signal, said sub-audio frequency operational amplifier connected to provide a sub-audio frequency amplification path to said output terminal. - View Dependent Claims (3, 4, 5, 6, 7)
-
-
8. A power amplifier for electrical signals in the audio frequency range, comprising:
-
an input stage including an audio frequency operational buffer amplifier having a pair of current supply ports, and connected in a voltage gain feedback circuit, one input of said operational amplifier being connected to receive an electrical input signal in the audio frequency range and its other input connected in said voltage gain feedback circuit, an output terminal, a pair of current mirrors connected to supply transient currents to respective operational amplifier current supply ports in response to changes in said input electrical signal, and to provide mirrored values of said transient currents, a charge storage means comprising a capacitance circuit connected between said current mirrors and the output of said operational amplifier to receive said mirrored currents and to adjust the voltage at said output terminal in response thereto, an output current gain stage connected in circuit between said signal storage means and said output terminal, and a current feedback circuit between said output terminal and said operational amplifier to assist voltage tracking between said output terminal and said electrical input signal.
-
-
9. A power amplifier for electrical signals in the audio frequency range, comprising:
-
an input stage including an audio frequency operational buffer amplifier having a pair of current supply ports, and connected in a voltage gain feedback circuit, one input of said operational amplifier being connected to receive an electrical input signal in the audio frequency range and its other input connected in said voltage gain feedback circuit, an output terminal, a pair of current mirrors connected to supply transient currents to respective operational amplifier current supply ports in response to changes in said input electrical signal, and to provide mirrored values of said transient currents, a charge storage means connected to receive said mirrored currents and to adjust the voltage at said output terminal in response thereto, an output current gain stage connected in circuit between said signal storage means and said output terminal, and a current feedback circuit between said output terminal and said operational amplifier to assist voltage tracking between said output terminal and said electrical input signal, said current feedback circuit being connected between said output terminal and the output of said operational amplifier.
-
-
10. A power amplifier for electrical signals in the audio frequency range, comprising:
-
an output terminal, a first operational amplifier connected to receive an electrical input signal in the audio frequency range and to provide an amplified version of said input signal to said output terminal, said first operational amplifier being connected in a current feedback circuit with said output terminal, and a second operational amplifier having a sub-audio crossover frequency and connected to provide an amplified version of sub-audio components of said input signal to said output terminal, said second amplifier dominating the first amplifier at said output terminal for components of the input signal having a frequency below said crossover frequency, said second sub-audio operational amplifier operating as an integrator and being connected in circuit with said output terminal in a voltage feedback circuit. - View Dependent Claims (11, 12, 13)
-
-
14. A power amplifier for electrical signals in the audio frequency range, comprising:
-
first and second operational amplifiers having respective inverting and non-inverting inputs, current supply ports, and outputs, means for applying an input signal to be amplified to the non-inverting input of the first operational amplifier, input circuitry for segregating the sub-audio components of said input signal and applying said sub-audio components to said second operational amplifier, said second operational amplifier being connected in an integrating local feedback circuit to amplify substantially only said sub-audio frequency components of said input signal, respective voltage feedback circuits providing voltage gains for said first and second operational amplifiers, a pair of nominally matched current mirrors having reference current ports connected to respective current supply ports of said first operational amplifier, and mirrored current ports, an output terminal, a capacitive circuit connected in circuit with said mirrored current ports and said first operational amplifier output to adjust the output terminal voltage in response to changes in said input signal, an output current gain stage connected between said capacitive circuit and said output terminal, a current feedback circuit between said output terminal and said first operational amplifier, a voltage feedback circuit between said output terminal and the local integrating feedback circuit for said second operational amplifier, said second operational amplifier and its associated feedback circuits dominating the output signal at said output terminal over a sub-audio frequency range, and means connecting the current supply ports of said second operational amplifier to provide offset cancellation currents to the current supply ports of said first operational amplifier, thereby tending to compensate for current mismatches between said current mirrors and to reduce the output offset voltage of the audio power amplifier. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
-
Specification