DB-linear variable gain amplifier (VGA) stage with a high broad band

1. A wide band variable gain amplifier (VGA) stage for amplifying or attenuating an input signal that is transmitted via a transmission line (H) comprising:

an operational amplifier for amplifying the input signal;

a feedback resistor connected to said operational amplifier and formed as a first series strip resistor having a first number of taps;

an input resistor arranged at an input of the VGA stage for attenuating the input signal and formed as a second series strip resistor having a second number of taps; and

a control device for switching said feedback resistor and said input resistor;

wherein said operational amplifier comprises a first operational amp portion for a positive half wave of the input signal and a second operational amp portion for a negative half wave of the input signal;

said feedback resistor comprises a first feedback resistor portion connected to said first operational amplifier portion and a second feedback resistor portion connected to said second operational amplifier portion; and

said input resistor comprises a first input resistor portion connected to an input of said first operational amplifier portion and a second input resistor portion connected to an input of said second operational amplifier.

2. A wide band variable gain amplifier (VGA) stage for amplifying or attenuating an input signal that is transmitted via a transmission line (H) comprising:

an operational amplifier for amplifying the input signal;

a feedback resistor connected to said operational amplifier and formed as a first series strip resistor having a first number of taps;

an input resistor arranged at an input of the VGA stage for attenuating the input signal and formed as a second series strip resistor having a second number of taps, wherein said second series strip resistor is arranged in parallel with a terminating resistor terminating the transmission line;

a control device for switching said feedback resistor and said input resistor; and

a switching device operative to utilize said input resistor as a second feedback resistor for said operational amplifier.

3. A wide band variable gain amplifier (VGA) stage for amplifying or attenuating an input signal that is transmitted via a transmission line (H) comprising:

an operational amplifier for amplifying the input signal;

a feedback resistor connected to said operational amplifier and formed as a first series strip resistor having a first number of taps;

an input resistor arranged at an input of the VGA stage for attenuating the input signal and formed as a second series strip resistor having a second number of taps, wherein said second series strip resistor is arranged in parallel with a terminating resistor terminating the transmission line, wherein said first series strip resistor and said second series strip resistor are structurally identical; and

a control device for switching said feedback resistor and said input resistor.

4. The VGA of claim 2 , wherein said control device is further operative to switch between an attenuation mode of operation and an amplifying mode of operation.

5. The VGA of claim 2 , further comprising a compensating circuit operative to compensate for offset of an output signal of the VGA.

6. The VGA of claim 5 , wherein said compensation circuit is additionally operative to compensate for offset of one or more filter stages coupled to the VGA stage.

7. The VGA stage of claim 1 , further comprising a buffer coupled at a junction between said first input resistor portion and said second input resistor portion, said buffer providing a constant common mode voltage.

8. The VGA stage of claim 7 , wherein said buffer comprises a voltage follower.

9. The VGA stage of claim 2 , wherein said operational amplifier includes a stabilizing capacitance that can be varied in dependence on gain.

10. The VGA stage of claim 9 , wherein said stabilizing capacitance is reduced with increasing gain.

11. The VGA stage of claim 9 , further comprising a stabilizing capacitance control device operative to control said stabilizing capacitance.

12. The VGA stage of claim 2 , wherein said first number of taps and said second number of taps are terminated with a high impedance.

13. A receiver for digital signal transmission, said receiver comprising:

a signal input configured to receive an input signal;

a signal output;

an operational amplifier for amplifying the input signal;

a feedback resistor connected to said operational amplifier and formed as a first series strip resistor having a first number of taps;

an input resistor arranged at an input of a VGA stage for attenuating the input signal and formed as a second series strip resistor having a second number of taps; and a control device for switching said feedback resistor and said input resistor;

wherein said operational amplifier comprises a first operational amp portion for a positive half wave of the input signal and a second operational amp portion for a negative half wave of the input signal;

said feedback resistor comprises a first feedback resistor portion connected to said first operational amplifier portion and a second feedback resistor portion connected to said second operational amplifier portion; and

said input resistor comprises a first input resistor portion connected to an input of said first operational amplifier portion and a second input resistor portion connected to an input of said second operational amplifier.

14. The receiver of claim 13 , further comprising a switching device operative to utilize said input resistor as a second feedback resistor for said operational amplifier.

15. The receiver of claim 13 , wherein said first series strip resistor and said second series strip resistor are structurally identical.

16. The receiver of claim 13 , further comprising a compensating circuit operative to compensate for offset of an output signal of the VGA stage.