Author: Michael Koltai

Feedback Capacitor Low-Pass Filter Pitfalls

Adding a capacitor in parallel with the feedback resistor of an op amp is an easy way of accomplishing low- pass filtering. This technique works quite well in an inverting  amplifier (see the curves below) but not necessarily in a non-inverting amplifier. If the NI amplifier has high gain, the filtering is not bad– but inferior to the inverting case.  As the NI amplifier gain is reduced, the filter effectiveness suffers. In a gain of +2V/V, there is only 6dB of stopband attenuation. In a voltage-follower   (gain of +1V/V), there is no low- pass filtering at all! In each amplifier, the value of R2 was stepped logarithmically from 100 ohms to 100k.\e(x,2) (Circuit is created by Neil P. Albaugh, TI-Tucson )

Circuit for Demonstration of Pitfalls related with the Feedback Capacitor in Low-pass Filters 

Demonstration of Pitfalls related with the Feedback Capacitor in Low-pass Filters circuits

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA.

Click here to invoke TINACloud  and analyze the circuit yourself, or  watch our tutorial video to learn how to create and analyze this circuit with TINA off-line version now under Windows 10  or on-line with TINACloud.

You can send this link to any TINACloud customers and they can immediately load it by a single click and then run using TINACloud.

Download the FREE trial demo of TINA Design Suite and get

1. One year free access to TINACloud (the cloud-based, multi-language, installation-free online version of TINA now running in your browser anywhere in the world.)
2. An immediate 20% discount from the offline version of TINA
3. Free license for your second computer, laptop etc.

Michael Koltai
www.tina.com

High Common Mode Voltage Difference Amplifier circuit

Achieving a high common mode voltage differential amplifier requires a very high attenuation resistor network.

To minimize op amp input offset voltage and drift errors, an autozero type is used– OPA735.  An OPA335 can be used on a 5V supply. Common- mode rejection is critically dependent on the ratio matching of R3:R2 & R4:R1. These should be matched to extremely tight tolerances. Power dissipation in R3 & R4 are significant. Bypass capacitors are not shown.  (Circuit is created by Neil P. Albaugh  TI – Tucson)

High Common-Mode Voltage Difference Amplifier circuit:

Creation and Simulation of a 1 kV High Common-Mode Voltage Difference Amplifier circuit

Watch our tutorial video to learn how to create and analyze this circuit with TINA off-line version  or on-line with TINACloud

Also if you download  the FREE trial demo of TINA Design Suite you can not only find and run this circuit but you will also get

1. 1. An immediate 20% discount from the offline version of TINA Design Suite
   2. Free license for your second computer, laptop etc.
   3. One year free access to TINACloud (the cloud-based, multi-language, installation-free online version of TINA now running in your browser anywhere in the world)

Click here  to download the FREE trial demo of TINA  Design Suite

Michael Koltai
www.tina.com

Creation and Simulation of an OPA569 Laser Driver Circuit

The “OPA569 Laser Driver” circuit provides voltage- controlled constant- current biasing of a grounded- anode laser diode by using a negative supply voltage and a positive control voltage. As shown, the OPA569 op amp provides an output current of 500mA per volt input. Output is current- limited to 2A by R2. Frequency compensation is provided by C3 R3. This circuit takes advantage of the unique topology of the OPA569; it does not require a shunt resistor to measure its output current. This amplifier provides an output monitor current from pin 19 that is 1/475 th of its output current. This current is used as negative feedback to the amplifier’s inverting input (pin 5). A constant- current output is derived by this feedback.

Since no shunt resistor is required to measure output current, there is no reduction in output voltage compliance due to shunt resistor voltage drop and this circuit can swing its output voltage very close to its supply rail. This increases efficiency and reduces heat sinking requirements. In fact, supply voltage can be reduced to 3.3V for most laser diodes. The OPA569 features both a Current Limit (pin 4) and a Thermal Overtemp (pin 7) flag. These flags can be used to protect the amplifier and the Enable (pin 8) can be used to digitally control its status. (Circuit is created by Neil P. Albaugh, TI – Tucson)

OPA569 Laser Driver Circuit:

Creation and Simulation of an OPA569 Laser Driver Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA.

Click here to invoke TINACloud  and analyze the circuit yourself, or  watch our tutorial video!

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Do you know that TINACloud also has an even more powerful downloadable offline version called TINA Design Suite?
TINA Design Suite is fully compatible with TINACloud and you can create, edit or run the same circuits in both systems. You can also easily exchange circuits between TINA Design Suite and TINACloud.

Download the FREE trial demo of TINA Design Suite and get

1. One year free access to TINACloud (the cloud-based, multi-language, installation-free online version of TINA now running in your browser anywhere in the world.)
2. An immediate 20% discount from the offline version of TINA
3. Free license for your second computer, laptop etc.