In a preferred embodiment, the gain expansion in low power mode of a single chain PA is minimized by dynamically adjusting the output impedance of the bias circuit of each gain stage for each mode of operation. Instead of switching in a series attenuator or switching in additional feedback in the first gain stage of a single-chain PA to limit the gain at the increased quiescent current level, this embodiment achieves linear performance by adjusting the quiescent current in each stage to the minimum level that meets the target gain and then increasing the output resistance of the bias circuit of each gain stage in low power mode (LPM) to provide the appropriate level of negative feedback at the base of each amplifying HBT to linearize the gain versus power response.

The invention provides an amplifier for LCD, comprising: an operational amplification module and an amplitude-limiting module serially connected to the operational amplification module; the operational amplification module comprising: an operational amplifier, a first resistor, a second resistor, a capacitor, a sampling voltage input terminal, a first reference voltage input terminal and a compensation voltage output terminal; the amplitude-limiting module being connected serially between the capacitor and the second resistor, the amplitude-limiting module comprising a first Schottky diode and a second Schottky diode connected in parallel, and a second reference voltage input terminal connected between the first Schottky diode and the second Schottky diode; an anode of the first Schottky diode and a cathode of the second Schottky diode being both connected between the capacitor and the second resistor. The amplifier for LCD of the invention is stable and reliable.

The invention provides an amplifier for LCD, comprising: an operational amplification module and an amplitude-limiting module serially connected to the operational amplification module; the operational amplification module comprising: an operational amplifier, a first resistor, a second resistor, a capacitor, a sampling voltage input terminal, a first reference voltage input terminal and a compensation voltage output terminal; the amplitude-limiting module being connected serially between the capacitor and the second resistor, the amplitude-limiting module comprising a first Schottky diode and a second Schottky diode connected in parallel, and a second reference voltage input terminal connected between the first Schottky diode and the second Schottky diode; an anode of the first Schottky diode and a cathode of the second Schottky diode being both connected between the capacitor and the second resistor. The amplifier for LCD of the invention is stable and reliable.

A system including a transducer and an amplifier as well as a circuit which always has a high impedance at low voltages. In addition, at high voltages, the circuit has a high impedance at high frequencies but a low impedance at low frequencies. In biased transducers, this circuit may be used between the charge pump and the transducer. In general, the circuit may be provided in a signal path between the transducer and the amplifier. The circuit has as an advantage that at startup, low frequency signals at high intensities may overload the amplifier, whereas at operation, higher frequency signals are desired fed to the amplifier at the same intensity. This is facilitated by the circuit.

A system including a transducer and an amplifier as well as a circuit which always has a high impedance at low voltages. In addition, at high voltages, the circuit has a high impedance at high frequencies but a low impedance at low frequencies. In biased transducers, this circuit may be used between the charge pump and the transducer. In general, the circuit may be provided in a signal path between the transducer and the amplifier. The circuit has as an advantage that at startup, low frequency signals at high intensities may overload the amplifier, whereas at operation, higher frequency signals are desired fed to the amplifier at the same intensity. This is facilitated by the circuit.

A system including a transducer and an amplifier as well as a circuit which always has a high impedance at low voltages. In addition, at high voltages, the circuit has a high impedance at high frequencies but a low impedance at low frequencies. In biased transducers, this circuit may be used between the charge pump and the transducer. In general, the circuit may be provided in a signal path between the transducer and the amplifier. The circuit has as an advantage that at startup, low frequency signals at high intensities may overload the amplifier, whereas at operation, higher frequency signals are desired fed to the amplifier at the same intensity. This is facilitated by the circuit.

A system including a transducer and an amplifier as well as a circuit which always has a high impedance at low voltages. In addition, at high voltages, the circuit has a high impedance at high frequencies but a low impedance at low frequencies. In biased transducers, this circuit may be used between the charge pump and the transducer. In general, the circuit may be provided in a signal path between the transducer and the amplifier. The circuit has as an advantage that at startup, low frequency signals at high intensities may overload the amplifier, whereas at operation, higher frequency signals are desired fed to the amplifier at the same intensity. This is facilitated by the circuit.

A system including a transducer and an amplifier as well as a circuit which always has a high impedance at low voltages. In addition, at high voltages, the circuit has a high impedance at high frequencies but a low impedance at low frequencies. In biased transducers, this circuit may be used between the charge pump and the transducer. In general, the circuit may be provided in a signal path between the transducer and the amplifier. The circuit has as an advantage that at startup, low frequency signals at high intensities may overload the amplifier, whereas at operation, higher frequency signals are desired fed to the amplifier at the same intensity. This is facilitated by the circuit.

In a preferred embodiment, the gain expansion in low power mode of a single chain PA is minimized by dynamically adjusting the output impedance of the bias circuit of each gain stage for each mode of operation. Instead of switching in a series attenuator or switching in additional feedback in the first gain stage of a single-chain PA to limit the gain at the increased quiescent current level, this embodiment achieves linear performance by adjusting the quiescent current in each stage to the minimum level that meets the target gain and then increasing the output resistance of the bias circuit of each gain stage in low power mode (LPM) to provide the appropriate level of negative feedback at the base of each amplifying HBT to linearize the gain versus power response.

The high-speed and high-quality reception operation of a transimpedance amplifier of an optical communication module and a router including the same can be achieved. A preamplifier performs current/voltage conversion with respect to intersymbol interference due to bandwidth shortage of a laser diode. A threshold control circuit which generates positive and negative threshold voltages with respect to a center potential of an output signal, latch circuits, and a selector circuit are provided to the output of the preamplifier. An NRZ signal is received as a duobinary signal based on the sign determination result of the previous bit. The determination error rate of the latch circuits can thus be improved.