Protection circuit for extending headroom with off-chip inductors
View Patent ↗A protection circuit for extending the dynamic range of an amplifier circuit is described. Off-chip impedances, such as inductors, cause the output of the circuit to swing above and below the bias voltage. A protection circuit is included, either on-chip or off-chip, to protect the integrated circuit components if there is a fault condition in either of the off-chip impedances.
1. An electronic circuit assembly, comprising;
an electronic circuit;
a first impedance;
a second impedance;
wherein said electronic circuit has a positive output connected to a bias voltage through said first impedance, and a negative output connected to said bias voltage through said second impedance: and
means for raising a DC voltage at said positive output and said negative output without substantially effecting AC performance of said electronic circuit;
wherein said electronic circuit is disposed on a common substrate, and said means for raising said DC voltage is disposed external to said common substrate.
2. The electronic circuit assembly of claim 1 , wherein said means for raising said DC voltage includes a first off-chip impedance and a second off-chip impedance.
3. The electronic circuit assembly of claim 2 , wherein said first off-chip impedance is a first off-chip inductor and said second off-chip impedance is a second off-chip inductor.
4. The electronic circuit assembly of claim 2 , wherein said first off-chip impedance is a first ferrite bead and said second off-chip impedance is a second ferrite bead.
5. The electronic circuit assembly of claim 1 , wherein said electronic circuit is an amplifier.
6. The electronic circuit assembly of claim 5 , wherein said amplifier is comprised of a plurality of amplifier circuit assemblies, each of said plurality of amplifier circuit assemblies having a positive amplifier output and a negative amplifier output, each said positive amplifier outputs being combined into said positive output and each said negative amplifier outputs being combined into said negative output.
7. A method of extending dynamic range of an output of an electronic circuit having a positive output and a negative output, wherein a first on-chip impedance is connected between said positive output and a bias voltage of said electronic circuit and a second on-chip impedance is connected between said negative output and said bias voltage, comprising the steps of:
(1) connecting a first off-chip impedance between said positive output and the bias voltage; and
(2) connecting a second off-chip impedance between said negative output and said bias voltage, said bias voltage raising a DC voltage level at said positive and negative outputs through said corresponding first and second off-chip impedances.
8. The method of claim 7 , further comprising the steps of:
(3) connecting a common resistor between said bias voltage of said electronic circuit and a resistor port, wherein said resistor port is further connected to said first on-chip impedance and said second on-chip impedance; and
(4) connecting a common capacitor between said resistor port and a ground.
9. The method of claim 8 , wherein said first on-chip impedance is a first reactive load and said second on-chip impedance is a second reactive load.
10. The method of claim 7 , wherein at least one of said first off-chip impedance and said second off-chip impedance is a ferrite bead.
11. An electronic circuit assembly, comprising:
a substrate;
an electronic circuit disposed on said substrate, and
an on-chip impedance disposed on said substrate, wherein
said electronic circuit has an output connected to a bias voltage through said on-chip impedance, and
said output further being connected to said bias voltage through an off-chip impedance that is disposed external to said substrate, wherein said off-chip impedance raises a DC voltage of said output.
12. The electronic circuit assembly of claim 11 , wherein said on-chip impedance is comprised of an inductor and a resistor.
13. The electronic circuit assembly of claim 11 , wherein said off-chip impedance is an off-chip inductor.
14. The electronic circuit assembly of claim 11 , wherein said off-chip impedance is a ferrite bead.
15. The electronic circuit assembly of claim 11 , further comprising a common point resistor, wherein said common point resistor has a first port and a second port, said first port being connected to said bias voltage, and said second port being connected through said on-chip impedance to said output of said electronic circuit.
16. The electronic circuit assembly of claim 11 , wherein said second port of said common point resistor is further connected through a common capacitor to a second potential, wherein said second potential is substantially equal to a ground at a desired operating frequency range.
17. The electronic circuit assembly of claim 11 , wherein said electronic circuit is used in a cable modem.
18. The electronic circuit assembly of claim 11 , wherein said electronic circuit is used in a set-top box.
19. The electronic circuit assembly of claim 11 , wherein said electronic circuit is used in a television tuner.