Tuesday, May 22, 2018

LF398 - Monolithic Sample and Hold Circuit

The LF198/LF298/LF398  are monolithic sample-and-hold circuits which utilize BI-FET technology to obtain ultra-high dc accuracy with fast acquisition of signal and low droop rate.

LF398 - Monolithic Sample and Hold Circuit

Operating as a unity gain follower, dc gain accuracy is 0.002% typical and acquisition time is as low as 6 µs to 0.01%. A bipolar input stage is used to achieve low offset voltage and wide bandwidth. Input offset adjust is accomplished with a single pin, and does not degrade input offset drift.

LF398 - Monolithic Sample and Hold Circuit

The wide bandwidth allows the LF198 to be included inside the feedback loop of 1 MHz op amps without having stability problems. Input impedance of 1010Ohm allows high source impedances to be used without degrading accuracy.

P-channel junction FET's are combined with bipolar devices in the output amplifier to give droop rates as low as 5 mV/min with a 1 µF hold capacitor. The JFET's have much lower noise than MOS devices used in previous designs and do not exhibit high temperature instabilities. The overall design guarantees no feed-through from input to output in the hold mode, even for input signals equal to the supply voltages.

Monday, May 21, 2018

LM2575 - Buck Adjustable Switching Regulator

"The buck-boost regulator circuit delivers -5V output. I hoped this would a nice way to generate a negative voltage for e.g. an LCD-display. However this circuit requires component values that are similar to the buck regulator at high load."

The TI Datasheet Layout Guidelines

LM2575 Switching Regulator
LM2575 - Step-Down Adjustable Voltage Switching Regulator with Output Enable

The LM2575 represents a superior alternative to  popular three-terminal linear regulators. Due to its
high efficiency, it significantly reduces the size of the heat sink.

The device also offers internal frequency compensation, a fixed-frequency oscillator, cycle-by-cycle current limiting, and thermal shutdown.

Saturday, May 19, 2018

LM723 Power Electronics Workhorse

This is another versatile and flexible chip. I could design current sources, voltage to current transmitters, level translation and many more. You can think of applications beyond the Power Electronics Scope with this.

LM723 Power Electronics Workhorse

"The circuit provides internal current limiting. When the output current exceeds 150mA an external NPN or PNP pass element may be used. Provisions are made for adjustable current limiting and remote shutdown."

LM723 Power Electronics Workhorse

The LM723/LM723C is also useful in a wide range of other applications such as a shunt regulator, a current regulator or a temperature controller

Some Specs -

Input voltage up to 40V, Output voltage adjustable from 2 to 37V, Output current to 150mA without external pass transistor and Adjustable current limiting.

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