Thanks! I plan to put more stuff on this channel regularly in and around the main channel, maybe to dive deeper on some topics that would clutter main content, or just odd ball topics that probably wouldn't be a good fit on the other one.
What I found was with this op amp not being rail to rail, the max output was between 3.5 and 4v out of 5v so when I was biased to 2.5v the top would clip early. When I re-biased to be 1/2 of actual output swing I was able to use higher input before clipping.
@@gadgetsideload Hi, what the problem was that there is a DC bias on the Input signal which added with the AC signal and shifting the output causing it to hit the rails. When you have a single rail opamp with a virtual ground, the AC input signal has to swing around this point. The feedback on the amplifier will cause the inverting input to also be at the same bias point as the noninverting input. e.g with a split rail +/-12V the non-inverting will be connected to ground, due to the nature of the feedback the inverting input will maintain a point close to ground (virtual ground). The opamp wants the two inputs to be at the same voltage (ground) so as current flows from the input the output swings to supply a current equal and opposite to maintain the balance. By changing the feedback resistor to twice the input resistance value, then the output needs to swing twice the amount of the input to provide the equal and opposite current. Hence voltages gain of 2. Now if you add a DC bias from the input source with the AC signal superposed on this, the output has to swing to cancel the current caused by the dc offset and by the ac signal. So now the output will swing about a different DC point and the signal my hit one or both rails. This is why you need to block any DC component on the input with a cap. Remember the output from a uP pin switching at a frequency with a 50% duty cycle will have an apparent DC bias of ½ the uP supply voltage. Change the duty cycle and the apparent dc bias moves up and down, affectively a DAC. The opamp will amplify the DC on the input by the same AC gain. sorry about the long post but i hope this helps.
I'll probably try several scenarios for observation to see what happens when setting it up different ways. I forget how I even did the final schematic now! The good thing about simulations is it's easy to open the file and try new things compared to breadboarding it all again. If I ever get the energy to play with transistor amplifiers I'm sure there'll be lots of fun there...Maybe I should skip straight to vacuum tubes. I can borrow the high voltage from a guitar amp...
@@gadgetsideload I've got a radio with a valve PA, nothing like trying to measure something with 900V on the anode cap. much more fun to simulate that less painfull as well.
Another great video. You really know your stuff and present it in an easy to understand way.
Thanks! I plan to put more stuff on this channel regularly in and around the main channel, maybe to dive deeper on some topics that would clutter main content, or just odd ball topics that probably wouldn't be a good fit on the other one.
@@gadgetsideload sounds like a plan. I personally like more in-depth videos. Some may not, so good to keep them separate 🙂
You should keep the bias should be set to 1/2VCC to give you a max voltage swing on the output.
What I found was with this op amp not being rail to rail, the max output was between 3.5 and 4v out of 5v so when I was biased to 2.5v the top would clip early. When I re-biased to be 1/2 of actual output swing I was able to use higher input before clipping.
@@gadgetsideload Hi, what the problem was that there is a DC bias on the Input signal which added with the AC signal and shifting the output causing it to hit the rails. When you have a single rail opamp with a virtual ground, the AC input signal has to swing around this point. The feedback on the amplifier will cause the inverting input to also be at the same bias point as the noninverting input.
e.g with a split rail +/-12V the non-inverting will be connected to ground, due to the nature of the feedback the inverting input will maintain a point close to ground (virtual ground). The opamp wants the two inputs to be at the same voltage (ground) so as current flows from the input the output swings to supply a current equal and opposite to maintain the balance. By changing the feedback resistor to twice the input resistance value, then the output needs to swing twice the amount of the input to provide the equal and opposite current. Hence voltages gain of 2.
Now if you add a DC bias from the input source with the AC signal superposed on this, the output has to swing to cancel the current caused by the dc offset and by the ac signal. So now the output will swing about a different DC point and the signal my hit one or both rails.
This is why you need to block any DC component on the input with a cap.
Remember the output from a uP pin switching at a frequency with a 50% duty cycle will have an apparent DC bias of ½ the uP supply voltage. Change the duty cycle and the apparent dc bias moves up and down, affectively a DAC.
The opamp will amplify the DC on the input by the same AC gain.
sorry about the long post but i hope this helps.
I'll probably try several scenarios for observation to see what happens when setting it up different ways. I forget how I even did the final schematic now! The good thing about simulations is it's easy to open the file and try new things compared to breadboarding it all again.
If I ever get the energy to play with transistor amplifiers I'm sure there'll be lots of fun there...Maybe I should skip straight to vacuum tubes. I can borrow the high voltage from a guitar amp...
@@gadgetsideload I've got a radio with a valve PA, nothing like trying to measure something with 900V on the anode cap. much more fun to simulate that less painfull as well.
Thanks