Thomson-csf Semiconducteurs Specifiques

Thomson Composants Militaires Et Spatiaux

Atmel Grenoble

Jean-Francois Debroux

The invention relates to integrated electronic circuits, and notably to those comprising analog functions. The invention relates more particularly to a starter circuit designed to ensure the automatic start-up of a biasing circuit following an interruption in the operation of the latter. The starter circuit comprises, in an integrated circuit substrate of a first type of conductivity comprising at least one well of an opposite type of conductivity and a semiconductor region of the same type of conductivity as the substrate, formed within the well and forming a p-n junction with the well, a first transistor, or transistor for detecting the operating condition of the biasing circuit, connected to the biasing circuit so as to be in the on state when the biasing circuit is operating normally and turned off when it is not operating normally, this transistor being placed in series with the p-n junction between two power supply terminals, the semiconductor region being connected to one of the power supply terminals, the drain of the first transistor being connected to the well by a conductor and being connected to the gate of a second transistor, or restart activation transistor, the second transistor being turned off by the switching on of the first transistor and being turned on by the existence of leakage currents in the p-n junction when the first transistor is in the off state.

Integrated circuit with automatic start-up function

A variable gain amplifier which has n parallel-connected elementary amplifiers, and components for selecting j-order (j=1, 2, . . . , n) elementary amplifier according to the desired gain. Each elementary amplifier is of a common base type. The variable gain amplifier includes components that are used to obtain a low value input impedance that is independent of the gain of the selected elementary amplifier. The variable gain amplifier will find particular application at the input stages of amplification lines of receiving circuits which require noise performance characteristics.

Variable gain amplifier having n parallel-connected elementary amplifiers

A push-pull output stage for electronic integrated circuits includes two NPN transistors (Q1, Q2) connected in series between two supply terminals. The output (S) is the junction point of the transistors. A third NPN transistor (Q3) has its base and its collector connected respectively to the base and to the collector of Q1. Two current flow arms (R1, Q4 and R2, Q5) are formed, one to establish a current depending on the potential of the emitter of Q3 and the other to establish a current depending on the potential of the emitter of Q1. The arms are mounted in a current mirror arrangement, the second arm tending to copy the current of the first arm; the current mirror generating a current output (S2) representing a difference between the current set up in the second arm and the current copied from the first arm. This current output is used to control the conduction of the second transistor (Q2). Thus, there is obtained an output stage using exclusively NPN transistors and having, at the same time, greater linearity than that of prior art devices.

Push-pull output stage for amplifier in integrated circuit form

The invention relates to an amplifying circuit with controlled gain, the gain of which is an exponential function of a gain control voltage. The circuit includes two identical amplifiers A1 and A2, the first constituting the basic amplifying cell of the circuit (input Ie, output Is), and the second receiving a reference signal (Iref). The output from the second amplifier, which is the product of the input Iref times the gain G, serves as input to a feedback control loop for the gain G of the amplifiers. This loop receives a set point voltage Vc with a view to establishing a gain G which is an exponential function of Vc. A large-gain differential amplifier AD constitutes the core of this loop: the differential voltage between its inputs tends to be held at zero by the feedback control loop. According to the invention, an element (FTL) with logarithmic transfer function is inserted into the loop between the output of the second amplifier A2 and the input of the large-gain differential amplifier AD.

Amplifying circuit with exponential gain control

Disclosed is an amplifier circuit with gain controlled by a current or a voltage. It is sought to obtain a linear gain as a function of the set value current or voltage, whereas amplifiers with controlled gain usually have a non-linear variation of the gain as a function of gain control voltage. According to the invention, there is proposed an amplifier circuit with the particular feature of having two identical amplifiers with controlled gain: one receives the signal to be amplified and gives an amplified output signal; the other receives a reference voltage or current and gives an output which is compared with a signal with a set value of variation in gain. The result of the comparison is used to automatically control the gain of the second amplifier to adjust its output to a desired value. The first amplifier receives the same automatic control signal as the second one. The second amplifier has its output automatically linked to a set value while, at the same time, having a fixed voltage or current as an input signal. It therefore has a known gain proportionate to the set value. Finally, the first amplifier, which is identical to the second one and receives the same gain control signal, thus has a gain proportionate to the set value, in accordance with what was desired.

Growing community of inventors

St Etienne de St Geoirs, France

Jean-Francois Debroux