Analog Devices,inc.

JoAnn P Close

Nathan R Carter

David Hall Whitney

Jennifer W Pierdomenico

Lewis W Counts

Vikram Garg

Apparatus and methods to increase the range of a signal processing circuit. A system uses floating bias circuits coupled to a signal processing circuit to increase the range of power supplies that can be used with the signal processing circuit, while maintaining the components of the signal processing circuit within a breakdown voltage threshold. As the voltage level of the data signal varies, the voltage level of the floating bias circuits varies as well.

Circuits with floating bias

The invention is directed to an amplifier including an absolute value circuit. The absolute value circuit may be driven by differential potentials and may include a first pair of transistors modulating a tail current of the amplifier when a differential input voltage goes high, and a second pair of transistors modulating the tail current of the amplifier when a differential input voltage goes low.

Differentially compensated input pair

A bipolar rail-to-rail input stage includes complementary differential input pairs, and a switching circuit which makes one or the other of the input pairs active depending on the relationship between a transition threshold voltage V and the common mode input voltage V . A transition threshold voltage selection circuit provides a selectable one of at least two different V voltages to the switching circuit in response to a select signal. In one embodiment, the select signal has logic &ldquo;high&rdquo;, logic &ldquo;low&rdquo;, and &ldquo;floating&rdquo; states. The transition threshold voltage selection circuit provides a first V voltage when the select signal is in a first state, a second V voltage when the select signal is in a second state, and disables the input stage when the select signal is in a third state.

Bipolar rail-to-rail input stage with selectable transition threshold

A rail-to-rail op amp output stage is configured to provide one or more additional base drive paths for each of its output transistors, reducing the stage's distortion and increasing its maximum output current without substantially increasing quiescent current. The additional base drive paths reduce the demand on the transistors driving the output transistors, lowering the distortion they might otherwise contribute to the output current. In a preferred embodiment, the collectors of the stage's clamp transistors are connected to the bases of their opposing output transistors, so that each clamp transistor provides an additional base drive path to a respective output transistor, thereby increasing maximum output current without substantially increasing quiescent current, and substantially reducing crossover distortion.

High output current operational amplifier output stage

A monolithic IC chip having a differential amplifier comprising a pair of JFETs with their top and back gates electrically isolated to provide a low-leakage-current input to the top gates. The amplifier includes independent bias circuitry for setting the potentials of the JFET back gates to a level close to that of the top gates. This circuitry includes resistive means coupled to the source electrodes of the input JFETs, and operable to establish a low-noise bias point for the back gates. The bias circuitry includes a reference current source comprising a pair of JFETs identical to the input JFETs and arranged to provide a gate-to-source voltage to match that of the input JFETs.

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Los Altos, CA, United States of America

JoAnn P Close