Hello! I have a non-inverting amplifier that works just as I'd like it to: a 20dB (10x) gain in voltage for a pulsed, positive signal. However, when I attach a voltage buffer, a) the gain drops, b) also becomes dependent on voltage level.
For example, if my input is 200 mV, the output is 2 V without the buffer (as expected), but 1.2 V with the buffer—a gain of 15.6 dB. For an input of 780 mV, the output is 7V—a gain of 19.1 dB.
If anyone could shed some light on a potential solution, I'd love to hear it! Thanks for reading, and my circuit specs are below.
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MY CIRCUIT:
- The input signal will range from tens of mV up to around 1.5 V. My supply voltage is about 16 V.
- This non-inverting amp design: http://www.play-hookey.com/analog/non-inverting_amplifier.html. I'm using Rz=24 Ω, Rf=820 kΩ, Rin=91 kΩ, and a LM358 op-amp.
- This voltage buffer design: http://www.circuitstoday.com/wp-content/uploads/2011/11/voltage-follower-using-transistor.png. I'm using a PN2222 transistor and RE=820 kΩ
- My load resistance is 50 Ω.
For example, if my input is 200 mV, the output is 2 V without the buffer (as expected), but 1.2 V with the buffer—a gain of 15.6 dB. For an input of 780 mV, the output is 7V—a gain of 19.1 dB.
If anyone could shed some light on a potential solution, I'd love to hear it! Thanks for reading, and my circuit specs are below.
-----------------------------------
MY CIRCUIT:
- The input signal will range from tens of mV up to around 1.5 V. My supply voltage is about 16 V.
- This non-inverting amp design: http://www.play-hookey.com/analog/non-inverting_amplifier.html. I'm using Rz=24 Ω, Rf=820 kΩ, Rin=91 kΩ, and a LM358 op-amp.
- This voltage buffer design: http://www.circuitstoday.com/wp-content/uploads/2011/11/voltage-follower-using-transistor.png. I'm using a PN2222 transistor and RE=820 kΩ
- My load resistance is 50 Ω.
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