Automatic gain control circuit and signal reproducing device
View Patent ↗In a signal reproducing device, for securing the stability in the steady state while enhancing the response of automatic gain control, a variable gain amplifier 109 adjusts the amplitude of a reproduction signal outputted from a head amplifier 108 . A gain control section 112 increases/decreases the gain in the variable gain amplifier 109 by a predetermined change amount according to the large-small relationship of the comparison result outputted from a comparator 111 . The gain change amount control circuit 113 controls the change amount of the gain in the gain control section 112 according to the frequency of inversion of the large-small relationship of the comparison result outputted from the comparator 111.
1. An automatic gain control circuit for amplifying an input signal, comprising:
a variable gain amplifier for amplifying an input signal with a variable gain;
an amplitude detection circuit for detecting the amplitude of the input signal;
a gain control section for controlling the gain according to the amplitude of the input signal; and
a gain change amount control circuit for controlling a change amount of the gain controlled, according to frequency of increase/decrease of the gain caused by the control.
2. The automatic gain control circuit of claim 1 , wherein the gain change amount control circuit performs at least either control of reducing the gain change amount when the frequency of increase/decrease of the gain is larger than a predetermined value or control of increasing the gain change amount when the frequency of increase/decrease of the gain is smaller than a predetermined value.
3. The automatic gain control circuit of claim 2 , wherein the gain change amount control circuit performs either control of reducing the gain change amount within a predetermined lower limit when the frequency of increase/decrease of the gain is larger than a predetermined value or control of increasing the gain change amount within a predetermined upper limit when the frequency of increase/decrease of the gain is smaller than a predetermined value.
4. The automatic gain control circuit of claim 1 , wherein the gain change amount control circuit determines the frequency of increase/decrease of the gain based on the amplitude of the input signal.
5. A signal reproducing device for amplifying a reproduction signal reproduced from a recording medium, comprising the automatic gain control circuit of claim 1 for amplifying the reproduction signal.
6. The signal reproducing device of claim 5 , further comprising an error detection circuit for detecting at least one error among a focus error, a tracking error and a defect of the reproduction signal,
wherein the gain change amount control circuit reduces the change amount of the gain when the frequency of increase/decrease of the gain is larger than a predetermined value, and if any of the errors is detected, turns the gain change amount back to a predetermined initial value.
7. An automatic gain control circuit for amplifying an input signal, comprising:
a variable gain amplifier for amplifying an input signal with a variable gain;
an amplitude detection circuit for detecting the amplitude of the input signal;
a gain control section for controlling the gain according to the amplitude of the input signal; and
a dead zone control circuit for controlling the width of an amplitude detection dead zone in the amplitude detection circuit according to frequency of increase/decrease of the gain caused by the control.
8. The automatic gain control circuit of claim 7 , wherein the dead zone control circuit performs at least control of widening the dead zone when the frequency of increase/decrease of the gain is larger than a predetermined value or control of narrowing the dead zone when the frequency of increase/decrease of the gain is smaller than a predetermined value.
9. The automatic gain control circuit of claim 8 , wherein the dead zone control circuit performs at least control of widening the dead zone within a predetermined upper limit when the frequency of increase/decrease of the gain is larger than a predetermined value or control of narrowing the dead zone within a predetermined lower limit when the frequency of increase/decrease of the gain is smaller than a predetermined value.
10. The automatic gain control circuit of claim 7 , wherein the dead zone control circuit determines the frequency of increase/decrease of the gain based on the amplitude of the input signal.
11. A signal reproducing device for amplifying a reproduction signal reproduced from a recording medium, comprising the automatic gain control circuit of claim 7 for amplifying the reproduction signal.
12. The signal reproducing device of claim 11 , further comprising an error detection circuit for detecting at least one error among a focus error, a tracking error and a defect of the reproduction signal,
wherein the dead zone control circuit widens the dead zone when the frequency of increase/decrease of the gain is larger than a predetermined value, and if any of the errors is detected, turns the width of the dead zone back to a predetermined initial value.