A bipolar or field-effect transistor amplifier with very large dynamic range for use as a preamplifier in a radio receiver, optical link reciver, or the like. The amount of gain is approximately an integral number. Diode-connected transistors in the collector load circuitry of a gain-providing transistor cancel the distortion from the non-linear effects of the emitter-base junction of the gain-providing transistor at high input signal levels. The number of diodes corresponds to the amount of gain desired. To reduce the noise generated by the amplifier, the emitter of the gain-providing transistor has an inductor in series therewith and the collector load circuitry has an inductor therein, the ratio of the inductances substantially determining the gain of the amplifier.
A radio frequency (RF) driver amplifier system and method that provides linear in decibel gain control is provided. The RF driver amplifier system comprises a linear transconductor receiving an input voltage and providing a controlled current based on input voltage received, temperature compensation circuitry for varying current from the linear transconductor according to absolute temperature, an exponential current controller receiving current varied according to temperature and providing an exponential current in response, and an inductive degeneration compensator receiving exponential current and providing a control current to driver amplifier circuitry, thereby compensating for inductive degeneration due to at least one inductor in the driver amplifier circuitry. Control current passes from the inductive degeneration compensator to the driver amplifier circuitry. Output gain from the driver amplifier circuitry varies linearly in decibels with respect to the input voltage.
Transimpedance amplifier having an input stage (1) to which an input current to be amplified is fed and an output stage (2) which outputs an output voltage (u.sub.o) corresponding to the amplified input current. By means of a current control circuit (4) the current (I.sub.c) flowing through the amplifying element (Q.sub.1) of the input stage (1) is detected and controlled in such a way that said current is independent of the ambient temperature and of the supply voltage (V.sub.cc). To detect the current (I.sub.c) a dummy transimpedance amplifier (5) is used in combination with a current mirror circuit (6), the current (I.sub.c) being controlled in that the control voltage (U.sub.c) of a further transistor (Q.sub.c) coupled to the amplifying element (Q.sub.1) configured as a transistor is adjusted accordingly.
A circuit for at least substantially eliminating at least one external interference signal from a radio communications signal received by a code division multiple access (CDMA) mobile phone including a receiving terminal and a low noise amplifier comprises: a plurality of damping devices operatively coupled between the receiving terminal and the low noise amplifier; a plurality of switches respectively operatively coupled between the plurality of damping devices and the receiving terminal; an interference detector operatively coupled to the receiving terminal for detecting the at least one external interference signal from the received radio communications signal; and a switch driver operatively coupled between the plurality of switches and the interference detector, the switch driver generating a switching signal in response to the interference detector to select at least one of the switches in accordance with the at least one detected interference signal in order to vary a gain associated with the received communications signal in accordance with at least one of the damping devices.
A single bias block for a single or multiple low voltage RF circuits including one or more amplifiers and one or more single or double balanced mixers with compensation for temperature and integrated circuit process parameters. The power supply may be a lower voltage without sacrificing the dynamic range of the amplifier and/or mixer by applying full power supply voltage to the load with the bias applied to the base circuit through an operational amplifier and/or buffer circuit. For the mixer, a lower noise figure may also be realized by moving the gain control impedance from the emitter to the collector circuit. The circuits may be discrete components or part of an integrated circuit. Methods are disclosed for reducing the power supply voltage without affecting the dynamic range of an amplifier, for temperature and process parameter compensation, and for controlling the gain of a mixer without affecting input or output impedance.
DOS application programs are accommodated when using a controllerless modem by providing a virtual device driver. The virtual device driver emulates UART to UART communications and handles interrupts by the DOS applications and by a hardware port managed by the controllerless modem. In one implementation, the virtual device driver shares a communications interface in common with 32-bit applications. In a communication system environment, DOS applications can participate in modem to modem communications with remote DTEs and with other devices using the services of the virtual device driver.
