Micro Linear Corporation

Intersil Americas Inc.

Micrel, Incorporated

Carlos A Laber

Paul R Gray

Martin J Alter

Robert Stephen Wrathall

Gwilym Francis Luff

Charles Vinn

Hoa Vu

Bhupendra K Ahuja

Stephen McCormack

Rohit Mittal

Robert Zucker

David Ritter

A circuit and corresponding method for a precision floating gate voltage reference that uses a feedback loop, conduction of tunnel devices, and a bandgap cell to accurately program a desired charge level on a floating gate and provide a predictable and programmable temperature coefficient parameter for such voltage reference. In one embodiment, a bandgap cell is coupled through a capacitor to the floating gate storage node for providing a voltage source for canceling the temperature coefficient (TC) of the storage capacitor. The circuit and method enables TC to be minimized by either choosing the proper voltage source characteristics or alternatively, by choosing the proper ratio of two capacitors. The bandgap cell can alternatively be designed to have positive TC (PTAT voltage sources) or negative TC (VBE junction).

Precision floating gate reference temperature coefficient compensation circuit and method

The invention is an improved implementation of an active-RC polyphase band-pass filter with transconductor cross-coupling between filter sections. The polyphase filter has first to fourth inputs, first to fourth outputs, two filter sections, and a block of transconductor pairs. The four input signals to the polyphase filter succeed one another in phase by 90 degrees. The two filter sections have reactances comprised of active balanced operational amplifiers with matched capacitors in their feedback loops. The block of transconductor pairs is coupled between corresponding reactances of each filter. The transconductance of each transconductor pair is set as the product of a desired radian center frequency and the capacitance of the corresponding matched capacitors. In the preferred embodiment, the transconductors are Gm cells and the transconductance of at least one Gm cell is field adjustable. The filter sections of the preferred embodiment can be a pair of low-pass third-order active-RC gaussian filters or a pair of low-pass sixth-order active-RC gaussian filters.

Active polyphase filter with transconductor cross-coupling of filter sections

An integrated circuit fabrication process includes a selective substrate implant process to effectively decouple a first power supply connection from a second power supply connection while providing immunity against parasitic effects. In one embodiment, the selective substrate implant process forms heavily doped p-type regions only under P-wells in which noise producing circuitry are built. The noisy ground connection for these P-wells are decoupled from the quiet ground connection for others P-wells not connected to any heavily doped regions and in which noise sensitive circuitry are built. The selective substrate implant process of the present invention has particular applications in forming CMOS analog integrated circuits where it is important to decouple the analog ground for sensitive analog circuitry from the often noisy digital grounds of the digital and power switching circuitry.

Selective substrate implant process for decoupling analog and digital grounds

A two-stage differential to single-ended amplifier. The input stage converts a differential voltage to a differential current. A first pair of bipolar input transistors are biased with constant currents. Therefore, their on-resistance does not affect gain linearity. Changes in input voltages induce currents in a first pair of field effect transistors (FETs) each having a gate coupled to the collector of a corresponding input transistor and a drain coupled to the emitter of the corresponding input transistor. Differential currents are provided to the output stage by a second pair of FETs, each configured to mirror the current in a corresponding one of the first pair of FETs. Gain is adjustable by enabling additional pairs of FETs configured as current mirrors. The output stage includes a second pair of bipolar transistors with bases coupled together and biased with equal currents. Currents from the input stage are applied to the emitters of the second pair of bipolar transistors. A third pair of FETs are coupled to the second pair of bipolar transistors forming a current mirror which tends to equalize the currents from the input stage. A current representative of a sum of currents from the input stage is forced through a resistor, forming the output voltage. The output voltage DC level is adjusted by controlling the voltage at the bases of the second pair of bipolar transistors.

Differential to single-ended video cable driver having BICMOS

An operational amplifier having an input and an output stage. The input stage includes first and second source-coupled NMOS input transistors for accepting a differential input voltage and first and second PMOS load transistors for supplying current to each input transistor. A node between the first input transistor and first load transistor is coupled to a gate of a third PMOS transistor having its source coupled to a positive supply and its drain coupled to the sources of the input transistors and to a negative supply through a first biasing transistor. The output stage includes a fourth PMOS transistor having its gate coupled to a node between the second input transistor and the second load transistor and a source coupled to the positive supply voltage. A drain of the output transistor forms an output node and is coupled to the negative supply through a second biasing transistor. To minimize the input offset voltage, a ratio of the width-to-length of the third PMOS transistor to the width-to-length of the fourth PMOS transistor equals to a ratio of a quiescent drain current in the third PMOS transistor to a quiescent drain current in the fourth PMOS transistor. The load transistors have relatively large lengths for high gain while the third and fourth PMOS transistors have small lengths for high speed. Therefore, the operational amplifier has low input offset voltage, high speed and high gain.

Differential to single ended conversion technique for an operational

A fast parasitic-insensitive continuous-time filter and equalizer integrated circuit that uses an active integrator is described. Circuit techniques for excess-phase cancellation, and for setting the corner-frequency of the filter and equalizer are also described. These techniques result in a filter and equalizer chip with performance independent of process, supply, and temperature without employing phase-lock loops. This 20MHz 6th order Bessel filter and 2nd order equalizer operate from 5V, and generate only 0.24% (-52dB) of total harmonic distortion when processing 2Vp-p differential output signals. The device is optimized to limit high-frequency noise and to amplitude equalize the data pulses in hard disk read-channel systems. The device supports data rates of up to 36Mbps, and is built in a 1.5 .mu./4GHz BiCMOS technology.

Circuit technique that sets transconductance

A fast parasitic-insensitive continuous-time filter and equalizer integrated circuit uses an active integrator. The integrator has a left-half plane pole. A feedback path is provided that includes a resistive impedance which comprises a MOS transistor operated in the triode region. The resistive impedance is adjustable for cancelling the pole. The feedback path also includes a capacitive impedance coupled in series with the resistive impedance.

Differential amplifier based integrator having a left-half plane pole

A fast parasitic-insensitive continuous-time filter and equalizer integrated circuit that uses an active integrator is described. Circuit techniques for excess-phase cancellation, and for setting the corner-frequency of the filter and equalizer are also described. These techniques result in a filter and equalizer chip with performance independent of process, supply, and temperature without employing phase-lock loops. This 20MHz 6th order Bessel filter and 2nd order equalizer operate from 5V, and generate only 0.24% (-52 dB) of total harmonic distortion when processing 2 Vp-p differential output signals. The device is optimized to limit high-frequency noise and to amplitude equalize the data pulses in hard disk read-channel systems. The device supports data rates of up to 36 Mbps, and is built in a 1.5.mu./4 GHz BiCMOS technology.

Slimmer circuit technique

This invention is for a transconductance amplifier. The amplifier has an amplifier input and an amplifier output with an amplifier output impedance. An input stage of the amplifier has a first transconductance. An intermediate state is coupled to the amplifier output through positive feedback. The intermediate stage has a second transconductance and an intermediate stage output having an intermediate output impedance. The gain of the amplifier is a function of the first transconductance times the second transconductance times the amplifier output impedance times the intermediate output impedance.

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Los Altos, CA, United States of America

Carlos A Laber