CHROMA AMPLIFIER FOR A COLOR RECEIVER

• US 3,586,765 A
• Filed: 06/27/1969
• Issued: 06/22/1971
• Est. Priority Date: 06/27/1969
• Status: Expired due to Term

• Current Assignee: Howard F. Jirka
• Original Assignee: Howard F. Jirka
• Inventors: Jirka, Howard F.
• Application Number:
  US04/837,022
• Time in Patent Office: 725 Days
• US Class Current: 348/644
• CPC Class Codes: H04N 9/71 combined with colour gain control

Abstract

A chroma amplifier and color killer has three transistor devices arranged in a Y-type circuit with two of the devices defining a cascode amplifier while the three collectively define a differential amplifier. Another cluster of similar devices define a second cascode amplifier which is in cascade with the first and further define a second differential amplifier. The chroma signal is amplified in both cascode amplifiers for delivery to the color demodulator. A color killer connects between the two differential amplifiers and has a threshold which is exceeded when the gain of the first cascode amplifier is above a particular value. Upon such occurrence, the color killer disables the second differential amplifier to interrupt translation of the chroma signal.

Claims

1. A chroma amplifier and color-killer system for a color receiver for utilizing a chroma carrier signal modulated with color-image information and for further utilizing a control signal having amplitude variations which represent intensity variations of said chroma signal, which system comprises:

a cluster of three signal translating devices arranged in a Ytype circuit configuration to define a cascode amplifier including one of said devices connected in cascode with one of the remaining two devices and further to define a differential amplifier in which said one device is included in the signal paths of both of said remaining two devices;

a second amplifier coupled in cascade with said cascode amplifier of said cluster and having a control circuit responsive to an applied killer signal for effectively disabling said second amplifier;

means for applying said chroma signal to said cascode amplifier of said cluster and for deriving an amplified chroma signal from said second amplifier;

means for applying said control signal to at least one of said remaining two devices of said cluster to control the amplification of said chroma signal;

a color-killer circuit having an input and an output and responsive to a control potential applied to said input and exceeding a given threshold value for developing a killer signal at said output;

means for connecting the input of said color killer to one of said remaining two devices of said cluster to receive therefrom a control potential exceeding said threshold level during operating intervals when the gain of the cascode amplifier of said cluster exceeds a preselected value; and

means for connecting the output of said color killer to said control circuit of said second amplifier to interrupt translation of said chroma signal during said operating intervals.

2. A chroma amplifier and color-killer system in accordance with claim 1 in which:

said second amplifier is a similar cluster of three signal translating devices arranged in a Y-type circuit configuration to define a second cascode amplifier and a second differential amplifier;

in which the cascode amplifiers of both clusters are connected in-cascade; and

in which said output of said color killer is connected to said second differential amplifier to interrupt signal translation in said second cascode amplifier during said operating intervals.

3. A chroma amplifier and color-killer system in accordance with claim 1 in which:

said control potential is applied differentially to both of said remaining two devices of said cluster of devices.

4. A chroma amplifier and color-killer system in accordance with claim 1 in which:

said input of said color killer is connected to the one of said remaining two devices of said cluster that is not included in said cascode amplifier.

5. A chroma amplifier and color-killer system in accordance with claim 4 in which:

said second amplifier is only AC coupled to said cascode amplifier while said color-killer input is DC coupled to the one of said devices of said cluster that is not included in said cascode amplifier.

6. A chroma amplifier and color-killer system in accordance with claim 1 in which:

said second amPlifier has a gain-control circuit including an adjustable color-saturation control for additional control of the amplification of said chroma signal; and

in which said second amplifier has a linear gain-control voltage characteristic.

7. A chroma amplifier and color-killer system in accordance with claim 6 in which:

said second amplifier is a similar cluster of three signal translating devices arranged in a Y-type circuit configuration to define a second cascode amplifier and a second differential amplifier;

in which the cascode amplifiers of both clusters are connected in-cascade;

in which said output of said color killer is connected to said second differential amplifier to interrupt signal translation in said second cascode amplifier during said operating intervals; and

in which said gain-control circuit of said second amplifier includes the one of the remaining two devices of the second cluster of devices that is not included in said second cascode amplifier.

8. A chroma amplifier and color-killer system in accordance with claim 7 in which:

said output of said color killer is connected to the one of said devices of said second cluster that is included in said gain-control circuit.

9. A chroma amplifier and color-killer system in accordance with claim 8 in which:

said input of said color killer is connected to the one of said devices of the first cluster of devices that is not included in said first cascode amplifier.

10. A gain-controlled chroma amplifier for a color receiver for utilizing a chroma carrier signal modulated with color-image information and for further utilizing a gain control signal comprising:

a cluster of three signal translating devices, including one having only two-electrodes and two having at least three-electrodes, arranged in a Y-type circuit configuration to define a cascode amplifier including one of said three-electrode devices and further to define a differential amplifier in which said one three-electrode device is included in the signal paths of both of the remaining devices;

means for applying said chroma signal to said one three-electrode device and for deriving an amplified chroma signal from said other three-electrode device; and

means for applying said gain-control signal to at least one of said devices, other than said one three-electrode device, to control the amplification of said chroma signal.

11. A gain-controlled chroma amplifier in accordance with claim 10 in which:

said gain-control signal is applied to said two-electrode device.

12. A gain-controlled chroma amplifier in accordance with claim 10 in which:

an adjustable color-saturation control develops said gain-control signal; and

in which said color-saturation control is unicontrolled with a contrast control for said color receiver.

13. A gain-controlled chroma amplifier for a color receiver for utilizing a chroma carrier signal modulated with color-image information and for further utilizing a gain control signal comprising:

a cluster of three signal translating devices, individually having input and output electrodes, arranged in a Y-type circuit configuration to define a cascode amplifier including one of said devices connected in cascode with one of the remaining two devices and further to define a differential amplifier in which said one device is included in the signal paths of both of said remaining two devices;

a feedback connection between said input and output electrodes of the other of said remaining two devices to provide feedback for said differential amplifier but not for said cascode amplifier;

means for applying said chroma signal to said one device and for deriving an amplified chroma signal from said one of said remaining two devices; and

means for applying said gain control signal to at least one of said remaining two devices, to control the amplification of said chroma signal.

14. A gain-controlled chroma amplifier in accordance with claim 13 in whiCh:

the parameters of said feedback circuit are proportioned to establish a substantially linear gain versus control signal characteristic for said chroma amplifier.

15. A gain-controlled chroma amplifier for a color receiver for utilizing a chroma carrier signal modulated with color-image information and for further utilizing a gain control signal comprising:

a cluster of three signal translating devices, individually having input and output electrodes, arranged in a Y-type circuit configuration to define a cascode amplifier including one of said devices connected in cascode with one of the remaining two devices and further to define a differential amplifier in which said one device is included in the signal paths of both of said remaining two devices;

means for applying said chroma signal to said one device;

means for applying said gain control signal to at least one of said remaining two devices to control the amplification of said chroma signal; and

means for deriving from said amplifier a first output signal comprising essentially only said chroma signal and a second output signal comprising essentially only said control signal.

16. A gain-controlled chroma amplifier in accordance with claim 15 in which:

said control signal has amplitude variations which represent intensity variations of said chroma signal; and

in which said control signal is applied differentially to said remaining two devices of said cluster.

17. A gain-controlled chroma amplifier in accordance with claim 16 in which:

said chroma output signal is derived from the one of said remaining two devices that is included in said cascode amplifier while said output control signal is derived from the other of said remaining two devices.