Analog summing and differencing circuit, optical receiving circuit, optical transmitting circuit, automatic gain control amplifier, automatic frequency compensation amplifier, and limiting amplifier

An analog circuit for receiving a differential pair of input signals and compensating for a direct-current offset therein, the differential pair of input signals including a first input signal and a second input signal with mutually opposite phases, the analog circuit comprising:

• a first peak-hold circuit receiving the first input signal and generating a first peak signal indicating a peak value of the first input signal;
• a second peak-hold circuit receiving the second input signal and generating a second peak signal indicating a peak value of the second input signal;
• a first differencing circuit receiving the first input signal and the second input signal and generating a first difference signal indicating an algebraic difference between the first input signal and the second input signal;
• a second differencing circuit receiving the first peak signal and the second peak signal and generating a second difference signal indicating an algebraic difference between the first peak signal and the second peak signal;
• and
• a first combining circuit for additively combining the first difference signal and the second difference signal,
• wherein the first differencing circuit includes a first amplifier receiving the first and second input signals as differential voltage inputs and generating a first single-ended voltage signal,
• the second differencing circuit includes a second amplifier receiving the first and second peak signals as differential voltage inputs and generating a second single-ended voltage signal, and
• the first combining circuit includes a differential amplifier receiving the first and second single-ended voltage signals.

An analog circuit for receiving a differential pair of input signals and compensating for a direct-current offset therein, the differential pair of input signals including a first input signal and a second input signal with mutually opposite phases, the analog circuit comprising:

• a first low pass filter filtering the first input signal and generating a first filtered signal;
• a first peak-hold circuit receiving the first filtered signal from the low pass filter and generating a first peak signal indicating a peak value of the first filtered signal;
• a second peak-hold circuit receiving the second input signal and generating a second peak signal indicating a peak value of the second input signal;
• and
• an analog summing and differencing circuit for additively combining the first input signal, the second input signal, the first peak signal, and the second peak signal to generate an offset-compensated differential pair of voltage output signals.

An analog circuit for receiving a differential pair of input signals and compensating for a direct-current offset therein, the differential pair of input signals including a first input signal and a second input signal with mutually opposite phases, the analog circuit comprising:

• a first peak-hold circuit receiving the first input signal and generating a first peak signal indicating a peak value of the first input signal, the first peak-hold circuit including a first capacitor for holding the peak value of the first input signal and a first discharging circuit for discharging the first capacitor;
• a second peak-hold circuit receiving the second input signal and generating a second peak signal indicating a peak value of the second input signal, the second peak-hold circuit including a second capacitor for holding the peak value of the second input signal and a second input discharging circuit for discharging the second capacitor;
• and
• an analog summing and differencing circuit for additively combining the first input signal, the second input signal, the first peak signal, and the second peak signal to generate an offset-compensated differential pair of voltage output signals.