OPA2134 at lower line impedance Rl

Hi, Stephen,

I am moving your post to the Precision Amplifier e2e where the apps engineers who support this product hang out.

-d2

Stephen,

The output voltage swing to the rail is a function of the output current, Iout, and thus three different load specified in OPA134 datasheet are good indication of one one may expect for other loads: for example, on dual +/-15 supply with load resistor connected to ground one gets:

Iout = -14.5V/10k = -1.45mA (output within 0.5V to negative rail)

Iout = -13.8V/2k = -6.9mA (output within 1.2V to negative rail)

Iout = -12.8V/600ohm = -21.5mA (output within 2.2V to negative rail), etc.

For other loads, please refer to the Output Voltage Swing vs Output Current graph below.  Please pay special attention to the short-circuit current limit of +/-40mA at 25C and ~+/-30mA at 125C since this is the point at which the output will become grossly distorted - your Iout must be kept below it.  

For example, with 300 ohm load and Vs=+/-15V, the output could swing +/12V and -11.4V at 25C - see above.

My client would like information based on Vin values of +4.5v and -4.5v  Do you have any information available based on those values?

Also where are you getting the voltage values for the Iout calculations above? are these numbers simply from the data sheet.  If so where can I find the voltage values for the other impedance levels

Stephen,

I have simulated OPA134  Output Voltage Swing vs Output Current for your specific power supply condition of Vs=+/-4.5V - see below:

I have also attached OPA134 macro-model you should use for any other specific condition you may need.  If you do not have the TINA-TI simulation tool, you may download it free by clicking on the following link: http://www.ti.com/tool/tina-ti?keyMatch=tina-ti&tisearch=Search-EN

Excellent, thank you for your help.  For the output current, earlier you listed values for 10k, 2k, and 600ohms were you solving for these or are they listed.  I'm wanting to know how I get the output current at 30, 100, and 300 ohms

in the first post you listed the output current by dividing a voltage value (which I assume came from the data sheet) by the line impedance (RL).

If i wanted to find the output current for 30, 100, and 300 ohms, or 50, 120, and 320 since I actually have a 20 ohm resistor on the output, how would I find those voltage values since they are not in the data sheet, or if those aren't available just knowing the output current so i can read the data on the voltage swing chart.

Stephen,

Since the load resistor is connected between Vout and ground (0V), I took the maximum output voltage, Vo, specified in the Open-Loop Gain condition column and calculated the output current simply using ohm's law:  Iout=(Vout-0V)/RL - see table below:

The same could be done for sourcing current by using positive output swing in the table above:

Iout = 13.8V/10k = 1.38mA (output within 1.2V to positve rail)

Iout = 13.5V/2k = 6.75mA (output within 1.5V to positive rail)

Iout = 12.5V/600ohm = 20.8mA (output within 2.5V to positive rail), etc.

But please use the simulation tool made available to you - it is there to help you.

This doesn't really answer my question and I'm not sure how to use the simulation tool to find this parameter.

the Vo condition is listed for those higher impedance values (on the datasheet)but it is NOT listed in the impedance levels that I need

namely, 50, 120, and 320 ohms.  Where can I find those maximum voltage values when using a +/- 4.5v supply so that I can figure out what my current output will be and in turn read the voltage swing values off of the chart you gave me.  I apologize that my lack of experience with TINA-TI prevents me from looking this up myself.

Stephen,

Below please find the OPA134 output voltage swings for resistive loads you have listed.

Also, I have attached the schematic used to simulate them - you need to learn how to use it.

thanks again, I hate to be a pain but I cannot read the numbers in those images, do you have a higher resolution version of the above image?

Stephen,

Do you think you could open up the schematic I sent you and click on pull-down menus: Analysis -> DC Analysis -> Calculate nodal voltages?  This will display the nodal voltages right on your schematic.  I have attached to this post a high resolution image just in case you run into problems.