Variable gain optical modulator with open collector driver amplifier and method of operation

1 . A distributed amplifier system comprising

an input configured to receive an input signal from a signal source;

an impedance matching network configured to match an input impedance to an output impedance of the signal source;

a DC block configured to block DC components in the input signal;

a variable gain amplifier configured to adjust the gain applied to the input signal based on a gain control signal to generate a gain adjusted signal;

an emitter follower circuit configured to receive and process the gain adjusted signal to introduce gain peaking to create a modified signal, wherein the gain peaking is configured to perform a frequency specific gain adjustment, and the emitter follower circuit comprises a variable current source configured to control the frequency specific gain adjustment; and

a distributed amplifier configured to receive the modified signal from the emitter follower circuit, the distributed amplifier configured to amplify the modified signal to create an amplified signal.

2 . The system of claim 1 further comprising an emitter follower stage located between the DC block and the variable gain amplifier.

3 . The system of claim 1 wherein the distributed amplifier is an open collector distributed amplifier.

4 . The system of claim 1 wherein the distributed amplifier includes a termination network and one or more impedance matching elements in the input path which are configured to perform gain shaping in the amplified signal.

5 . The system of claim 1 wherein the distributed amplifier includes two or more amplifier cells configured as cascode differential pair circuits.

6 . The system of claim 1 wherein the input signal to the distributed amplifier system is differential input signal.

7 . The system of claim 1 wherein the gain peaking introduced by the emitter follower circuit is controlled by a control signal supplied to the variable current source.

8 . The system of claim 1 wherein the distributed amplifier system is part of an optic signal transmitter.

9 . A method for processing and amplifying an input signal prior to transmission comprising:

impedance matching the input signal with an impedance matching network to reduce signal return loss;

reducing or eliminating DC signal components in the input signal with a DC block circuit;

adjusting the gain applied to the input signal with a variable gain amplifier to create a modified input signal;

processing the modified input signal with an emitter follower circuit, wherein the processing by the emitter follower circuit establishes gain peaking into the modified input signal, wherein the gain peaking performs a frequency specific gain adjustment, and the emitter follower circuit comprises a variable current source to control the frequency specific gain adjustment; and

receiving and amplifying the modified input signal with gain peaking with a distributed amplifier to create an amplified signal.

10 . The method of claim 9 wherein the distributed amplifier is configured with an open collector.

11 . The method of claim 9 further comprising performing impedance matching and gain peaking control with an emitter follower stage prior to adjusting the gain with the variable gain amplifier.

12 . The method of claim 9 wherein the DC block circuit comprises one or more capacitors.

13 . The method of claim 9 wherein the gain of the variable gain amplifier is based on a control signal provided to a variable current source.

14 . The method of claim 9 wherein the input signal is a differential signal, and the output signal is a differential signal.

15 . The method of claim 9 wherein the distributed amplifier includes two or more amplifier cells each configured as cascode differential pair circuits.

16 . An optic signal transmitter with distributed amplifier comprising:

an input configured to receive an input signal from a data source;

a driver and biasing module comprising:

one or more biasing circuits configured to generate one or more bias signals for the transmitter;

an impedance matching network configured to match an input impedance of the transmitter to an output impedance of the data source;

a variable gain amplifier configured to adjust a magnitude of the input signal based on a gain control signal to generate a gain adjusted signal;

an emitter follower circuit configured to receive and process the gain adjusted signal to introduce gain peaking, wherein the gain peaking is configured to perform a frequency specific gain adjustment, and the emitter follower circuit comprises a variable current source configured to control the frequency specific gain adjustment; and

a distributed amplifier configured to receive and amplify the gain adjusted signal with gain peaking, from the emitter follower circuit, to create an amplified signal; and

a modulator and optic signal generator configured to receive the amplified signal and convert the amplified signal to a modulated optic signal for transmission over an optic channel.

17 . The transmitter of claim 16 further comprising a DC block connected to an output of the impedance matching network, the DC block configured to block DC components in the input signal.

18 . The transmitter of claim 16 wherein the distributed amplifier is configured with an open collector.

19 . The transmitter of claim 16 wherein the gain of the variable gain amplifier is based on a control signal provided to a variable current source.

20 . The transmitter of claim 16 wherein the distributed amplifier includes two or more amplifier cells each configured as cascode differential pair circuits.