Abstract:
The system described comprises various circuit units (10, 11, 12) each having a capacitor (C0, C1, C2) and charging means (G0, G1, G2) for defining a quantity depending upon the ratio (I/C) between the charging current and the capacitance of the capacitors. In order to compensate automatically for deviations of the actual capacitances from the nominal capacitances due to fluctuations in the parameters of the integrated-circuit manufacturing process, the system has a phase-locked loop (PLL) which uses one (10) of the circuit units as an adjustable oscillator, and current transducer means (17) which regulate the charging currents of the capacitors (C1, C2) of the circuit units (11, 12) in dependence on the regulated charging current of the capacitor (C0) of the oscillator (10) or the error current of the PLL loop.
Abstract:
A BiCMOS Transconductor differential stage (10) for high frequency filters comprises an input circuit portion having signal inputs (IN+,IN-) and comprising a pair of MOS transistors (M1,M2) having their respective gate terminals (G1,G2) corresponding to the signal inputs as well as an output circuit portion having signal outputs (OUT-,OUT+) and comprising a pair of two-pole transistors (Q1,Q2) connected together with a common base in a circuit node (B) and inserted between inputs (IN+,IN-) and outputs (OUT-,OUT+) in cascode configuration. The stage (10) in accordance with the present invention calls for a switching device (3) associated with at least one of said added two-pole transistors (Q1,Q2) to change the connections between the parasite capacitors present in the transconductor stage. The switching device (3) also comprises at least one added two-pole transistor (Q1x, Q2x) connected in a removable manner in parallel with the corresponding two-pole cascode transistor (Q1,Q2). In a variant embodiment there are also provided respective added MOS transistors (M1x,M2x) connected in parallel with the MOS transistors (M1,M2) of the input portion to change the ratio W:L of each of the input transistors (M1,M2).
Abstract:
The amplifier described has an output stage constituted by an npn transistor (Q1) and a pnp transistor (Q2) in a push-pull arrangement, and a driver stage. The latter comprises a current-mirror circuit having, in its input branch, a pnp transistor (Q3) in series with a first constant-current generator (G1) and, in its output branch, an npn transistor (Q4), and two complementary transistors (Q5 and Q6) of which the collectors are connected together to the output terminal (OUT) and the bases are connected together to the input terminal (IN) of the amplifier. The emitter of the pnp transistor (Q5) of the driver stage is connected to the positive terminal (vdd) of the supply by means of a second constant-current generator (G2) and to the base of the npn transistor (Q1) of the output stage, and the emitter of the npn transistor (Q6) of the driver stage is connected to the negative terminal (gnd) of the supply by means of the npn transistor (Q4) of the output branch of the current-mirror circuit and to the base of the pnp transistor (Q2) of the output stage. The amplifier has a very low or zero offset ( Vos = Vout-Vin ).
Abstract:
A phase-locked circuit for regulating the frequency of a controllable oscillator (ICO2) at a preset value is described. It comprises a reference oscillator (ICO1) which generates a signal at the preset frequency, a phase detector (10) which receives the signals from the two oscillators and produces a phase error signal, and processing circuit means which can apply a signal which is a function of the magnitude and sign of the phase error at the regulating terminal of the controllable oscillator (ICO2). In order to enable the feedback loop to open for an indefinite period after a phase-locking while still maintain the frequency at the preset value, the processing circuit means comprise a counter (CNT) which numerically measures the phase error and a digital-to-analogue convertor (DAC) which produces an input signal corresponding to the numerical measurement.
Abstract:
A transconductor stage (1) for high-frequency filters (5), of a type which comprises an input circuit portion having signal inputs (A,B) and an output circuit portion, incorporates a pair of field-effect transistors (M1,M2) having respective gate (G1,G2) and source (S1,S2) terminals in common, and has the output portion formed of a pair of bipolar transistors (Q1,Q2) connected to the aforesaid field-effect transistors.
Abstract:
The invention relates to a basic cell (11) for comparing a first and a second digital signal (A, B), of the type having at least a first and a second input (I1, I2) and a first and a second output (O3, O4) and comprising at least one logic gate (14) receiving digital signals (A, B) at a first and a second signal input (IS1, IS2), and which comprises at least a first and a second controlled switch (P1, P2) inserted in parallel with each other between the output terminal of the logic gate (14) and the second output (O4) from the cell (11), the first switch (P1) being also connected between the first input (I1) and the first output (O3) of the cell (11) and the second switch (P2) being also connected between the second input (I2) and the second output (O4) of the cell (11). The invention also relates to a digital comparator (9) comprising a plurality of basic cells according to the invention.
Abstract:
An elementary cell structure for programmable time-continuous analog filters and in particular for the processing of analog signals in read/write operations on magnetic supports comprises an amplifier stage (3) provided with a pair of structurally identical transconductance half-cells (2,2') connected together in a common circuit node (X). With a cascade of cells of this type is provided a time-continuous analog delay line which is used in a transverse time-continuous analog filter. This filter comprises a cascade of identical delay lines (LR) connected through multiplier nodes (5) to a final summation node (6).
Abstract:
A digital/analog quadratic converter (DACQ) composed by a pair of linear converters connected in cascade has a direct coupling of the output node of the first converter (DAC1) with a node of a R-2R type resistive network of the second converter (DAC2) corresponding to the LSB stage of the R-2R type resistive network. High impedance nodes, notably the input node of the second linear converter, are advantageously eliminated from the "current path" thus markedly reducing the problems of relatively long settling times of high impedance nodes (having intrinsically large parasitic capacitances associated therewith). The peculiar architecture of the quadratic converter provides also for a remarkable simplification of the circuit.
Abstract:
A high-pass filter in particular for high-frequency applications and of the type comprising at least one input terminal (IN) and at least one output terminal (OUT) between which is defined a transfer function (FdT) and is inserted a biquadratic cell (18) incorporating a series of transconductance stages (2, 3, 4, 5) comprises a generator circuit (29) of variable currents (i K1 , i K2 ) connected between a pair of stages (2, 3) of the biquadratic cell (18) and a voltage reference (GND). Said generator allows introduction of programmable zeroes in the transfer function (FdT) of the filter (20).
Abstract:
A controlled gain transconductor (20) which comprises a transconductance stage (3) having at least two input terminals (I1, I2) and at least two output terminals (O1, O2), an active load (4) connected to the output terminals of the transconductance stage and a control circuit (5) for the active load (4) conneccted between said output terminals (O1, O2) and the active load (4). Also provided is a circuit portion (10) being a replica of the transconductance stage (3), the active load (4) and the control circuit (5). This replicated portion (10) has an output connected to the control circuit (5) of the transconductor (20) to provide a predetermined voltage value (Vc) required for adjusting the DC gain of the device.