delabs Circuits

Showing posts with label Analog-Design. Show all posts
Showing posts with label Analog-Design. Show all posts

Friday, February 05, 2016

LF353 - Wide Bandwidth Dual JFET

These devices are low cost, high speed, dual JFET input operational amplifiers with an internally trimmed input offset voltage (BI-FET II™ technology). They require low supply current yet maintain a large gain bandwidth product and fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents.

LF353 - Wide Bandwidth Dual JFET 

(Google Talk Transcript - Year 2006 )

Audio Tone Control with LF353 - Bass and Treble and Mid-Range(Presence). Bass is like Drums and Woofer. Treble is like Guitar and Tweeter. Mid-Range is like Vocal and Medium Speakers.

This circuit is to demonstrate the capability of the Opamp. The post is more related to instrumentation.

Audio Tone Control with LF353

TF (12:16:46 PM): i need a clarification on OpAmp
delabs (12:16:57 PM): ok tell me
TF (12:20:55 PM): what parameter should I check to know the frequency response of an Opamp
TF (12:20:55 PM): the thing is i am reading about a perfect rectifier
TF (12:20:55 PM): so i am trying to find out how to get its maximum frequency
delabs (12:21:14 PM): ok
delabs (12:22:02 PM): you mean precision rectifier
TF (12:48:56 PM): are u there sir
delabs (12:49:17 PM): national.com/mpf/LF/LF353.html
delabs (12:49:03 PM): These devices are low cost, high speed, dual JFET input operational amplifiers with an internally trimmed input offset voltage. They require low supply current yet maintain a large gain bandwidth product and fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents. The LF353 is pin compatible with the standard LM1558 allowing designers to immediately upgrade the overall performance of existing LM1558 and LM358 designs. These amplifiers may be used in applications such as high speed integrators, fast D/A converters, sample and hold circuits and many other circuits requiring low input offset voltage, low input bias current, high input impedance, high slew rate and wide bandwidth.
delabs (12:50:16 PM): Characteristics of Operational Amplifiers
TF (12:52:03 PM): checking
TF (12:52:26 PM): i think slew rate would be the parameter
delabs (12:52:42 PM): great, you got it

Wednesday, December 02, 2015

Power Oscillator Circuit Design

I am trying to find a circuit diagram for a long time, which will give me the o/p Characteristics as 12V, 0.5A & 4000 Hz (or variable frequency). Will you please help me in this regard? I will be very very thankful to you.

Mail from PS

First make an Oscillator and then Power Amplify it.

LM675 Power Operational Amplifier

"The LM675 is capable of delivering output currents in excess of 3 amps, operating at supply voltages of up to 60V. The device overload protection consists of both internal current limiting and thermal shutdown. The amplifier is also internally compensated for gains of 10 or greater. "

Op Amp Booster Designs  PDF

"The design of booster stages which achieve power gain while maintaining good dynamic performance is a difficult challenge. The circuitry for boosters will change with the application’s requirements, which can be very diverse. A typical current gain stage is shown in Figure 1."

Op Amp Booster Designs

12V, 0.5A & 4000 Hz (or variable frequency) is possible, very high frequencies difficult, for that you have to study RF behavior. Experiment from DC to 1 M Hz, no more with these circuits. 200/300 K Hz if you manage you learn't something. Study pages, learn and try to build it yourself. These links are for learning.

delabs

I am extremely thankful to you for your precious reply for my mail. I have tried it to complete the circuit as per your suggestion, but the results are not as per the requirements. Here, I tell you the exact situation. Sir, I am working on the efficiency improvement of an alternator. for this reason I need a frequency generator circuit which will give me the o/p characteristics as 12V, 0.5A & variable frequency upto 4000Hz. The signal must be AC sine waveform. It can be applicable to inductive load. The i/p will be simply 230V AC. Will you please design a circuit for such requirements?

I am in great need of this. Please, I request you to design it. I will be very very thankful to you.

Reply from from PS IN

For professional service, there will be design charge. Your reply will be posted. Anyone who can design this can comment here.

Unique IC Buffer Enhances Op Amp Designs, Tames Fast Amplifiers

A unity gain IC power buffer that uses NPN output transistors while avoiding the usual problems of quasi-complementary designs is described. F


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Sunday, December 14, 2014

Analog Ground and Digital Ground

I need a few tips from you on Analog design in general: I have seen that a lot of ADCs have a separate AGND and DGND, but they are shorted at the chip. I believe this is required to keep the noisy digital return paths sperate from the analog return paths.

However if both get shorted at the ADC what purpose will it serve? Do you know any good application notes which clarify this ?

mail from TF


Some ADCs have differential inputs which are some times not used. Strain gauge bridge amplifiers may need differential measurement. When common mode measurements are made one end can be grounded.

Compatible Electronics, Inc - Specialize in EMC testing for FCC as well as EMC / EMI testing for CE Mark compliance under the Electromagnetic Compatibility Directive.

Grounding Demystified - Seminar of Compatible Electronics Inc

Grounding Demystified - Seminar of Compatible Electronics, Inc

In Other ADCs the analog ground and digital ground may be shown shorted in circuit.

The digital ground carries the power current to digital circuits in the chip. This current will have pulses due to switching of many digital outputs. The short, wire or link shown is circuit is assumed to be ideal in design. In fact the short, wire or PCB track has resistance, capacitance and inductance. These small values of RLC in a PCB track can cause strange AF-RF behavior.

Staying Well Grounded Analog Devices

Successful PCB Grounding with Mixed-Signal Chips Maxim Integrated

The ideal is the digital ground should be a track going directly to supply ground. The analog ground should be a track linking to the measurement circuits or sensors. The analog and digital ground now should be linked close to chip. This link will carry no current, so no ground loop, so no lifting of ground.

This ground problem can reset microcontrollers or timers when a solenoid or relay operates. Similar problem produces hum, feedback oscillations in Audio systems.

Radiating grounds, ground planes, thick tracks, decoupling caps can be remedies. see this link too.

Noise and Hum in Audio Circuits

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