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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. 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.

LF398 – Monolithic Sample and Hold Circuit

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.

National Semiconductor is part of TI

National Semiconductor was an American semiconductor manufacturer, that specialized in analog devices and subsystems, formerly headquartered in Santa Clara, California, USA. The products of National Semiconductor included power management circuits, display drivers, audio and operational amplifiers, communication interface products and data conversion solutions.

Wiki of National Semiconductor

National’s key markets included wireless handsets, displays and a variety of broad electronics markets, including medical, automotive, industrial, and test and measurement applications.

National Semiconductor is part of TI

On September 23, 2011, the company formally became part of Texas Instruments as the “Silicon Valley” division.

An Exquisite Evaluation Board from National Semiconductor

The LMH0356 Serial Digital Interface (SDI) reclocker is designed to recover a clean clock from a serial digital video signal which may be contaminated by jitter and to resynchronize the input video data to the recovered clean clock. The LMH0356 SDI reclocker accepts signals conforming to standards SMPTE 259M (C), SMPTE 292M, and SMPTE 424M.

SPICE Analog Simulation Program TINA TI

TINA is an easy-to-use, but powerful, circuit simulation program based on a SPICE engine. TINA-TI is a fully functional version of TINA, loaded with a library of TI macromodels plus passive and active models.  TINA-TI’s new version 7.0 has changes from Version 6.0 in the following areas:

SPICE Analog Simulation Program TINA TI

SPICE Analog Simulation Program TINA TI

TINA-TI provides all the conventional DC, transient and frequency domain analysis of SPICE and much more. TINA has extensive post-processing capability that allows you to format results the way you want them. Virtual instruments allow you to select input waveforms and probe circuit nodes voltages and waveforms. TINA’s schematic capture is truly intuitive-a real “quickstart.”

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Two Stage Sequential Timer Docs

The circuit is a two stage sequential timer with auto reset. It can turn a Solenoid On/Off after a Sequence of delays that are preset. This is also a basic example of timer usage in automation.

Design Documents

Source Files Orcad Format

All Timers are 1 – 30 Secs Analog with Presets to adjust with a screwdriver. The Switch, Solenoids and Power supply has to be via terminal blocks or plug-jacks. The PCB may be upto six Square Inches for standard DIP components but with SMD it may be smaller.

Block Diagram :

Sequential Timer Specs

The PCB has to be tested to conform with the circuit, this has to be Meticulous. The Circuit is for the Battery and Solenoid Specified and will have to be modified if battery and solenoid are different. D1 to D4 can be replaced by a 300V 3A Bridge Rectifier Module. F1 fuse could be 2A – 3A Slow Blow depends on Solenoid inrush current. Presets can be with some graduations if possible for ease of adjustments. LED resistors can be a bit lower if more brightness is required.

Four Channel Temperature Alarm Docs

The temperature in a pipe is monitored with four RTD Pt-100 Sensors, The type of probe could be Extruder RTD probes with Bayonet or Compression Fitting, Get it from Omega. To keep costs low you can choose small thin film RTD sensors, they will be fast but on rough usage may break.

Design Documents

Source Files Orcad Format

The time taken to measure the temperature at the 4 points will be less than 4 seconds. An optional display of the measured temperature as shown above can be avoided by using a DMM to adjust the setpoint.

The Analog Timer Module can be set from 0- 30 minutes. If out-a remains high even after set time a out-b alarm goes on to sound a buzzer and flash a LED light.

Block Diagram :

Four Channel Temperature Alarm

It all started with a email from a client like this ……….

“I am looking at an idea for a circuit design; The idea is to sense a temp of 130 degrees and then light an LED and start a timer delay. The delay would be 3 min, after the delay if the temp is still above 130 sound alarm.

With the LED I would like to drive a counter display to show how many times the temp was sensed. I would like powered by 120vac and a 9 volt battery backup for counter circuit. If you can assist please let me know.”

Astable Multivibrator with 555

This is a demo of the popular 555 timer. you can try out the project on this page by a javascript simulation.Press the Red button below to turn on the circuit press it again to turn off. The 555 can source (LED2) or Sink (LED1) upto 200mA.

Screenshot of Astable 555 Timer Flasher

It can even drive a small motor or lamp with diodes added to protect from inductive kickback.Vary Ra, Rb and Ct with the controls given and see the change of frequency, period and duty cycle.


Astable Multivibrator with 555

Astable Multivibrator with 555

This is a tutorial with calculator to help learn the application of 555 which is a very rare chip innovation. It is simple, versatile, flexible and programmable (by tweaking of pots).

Simple WorkBench Dual Power Supply

I will just explain part of this circuit. D9 and D10 provide a low cost -1.4 from -5 V. This is needed to reach near 0.00 for LM317 Min. setting. An LED also can be used with proper bias. Note that there is a Temperature Coefficient in ppm,  but it may not matter upto 8 bits accuracy.

TIP2955, TIP3055 (NPN), TIP2955 (PNP) Complementary Silicon Power Transistors. It is a Darlington, that means good current gain. When current in R1 10E goes more than 50mA a voltage of 50mA X 10E = 500mV is applied across Emmiter-Base junction. So lower than 500mV no bias the tap is turned off, 500mV-700mV the tap starts turning on depending on type of transistor.

Power Supplies Section

The transistor is like a water Tap. So TIP2955 carries the major current burden thru the load allowing LM317 to do the decision making when to turn-on or off. It is analog control, it is not On-Off but linear-proportional. The LM317 is very cool as the burden is passed off to TIP2955 who will need a heatsink to keep going and deliver the power you want.

WorkBench Dual Power Supply

Put the filter caps appropriately. The Hum-Noise will be filtered. The cap after the regulator should be a small guy. The main filter cap after the Bridge can be as big as your cabinet or budget.

Mains Voltage Power Transformers

If you build it and wire it without designing a PCB, then make all wiring and connection very sound. The test of this ability you can know easily, If your project stops working after the last screw of the cabinet is tightened, Then we need to improve.