| ??? 06/28/05 04:08 Read: times |
#96071 - The circuit works, but... Responding to: ???'s previous message |
Thanks Kai!
======================== In order to prevent the circuit from oscillating, which is often caused by a positive feedback of output signal to input via stray capacitance, between each gain stage a low pass filter of 10k and 100pF is inserted. ======================== 
By testing the circuit on a breadboard I know what you mean above. Everytime I move the opamp output (the long orange wire) near any component of the first or second stage of the preamp the opamp starts oscillating. I've made some modification to the circuit because I don't have 39k and 62k resistors. 39k -> 10k + 30k 62k -> 69k That won't affect the effect of the circuit a lot, does it? I've add one more LM324 to the circuit you have given me because the output after 4 stages of amplify is still too weak. I use a diode, a cap and a LM339 to replace the transistor's place. The circuit is not very stable. Sometimes it keeps oscillating. I have to remove all the wires connected to the LM324 output to stop it from oscillating, and connect back again. How to prevent it from oscillating and what modification should be done if I use a LM318 instead of the LM324? Assume the negative voltage source is not a problem. Stanley |
| Topic | Author | Date |
| Ultrasonic Signal Processing | 01/01/70 00:00 | |
| Time dependant gain | 01/01/70 00:00 | |
| Further attenuation... | 01/01/70 00:00 | |
| Signal recovery. | 01/01/70 00:00 | |
| AGC? | 01/01/70 00:00 | |
| AGC as Steve said// | 01/01/70 00:00 | |
| My Algorithm was: | 01/01/70 00:00 | |
| My Algorithm was: | 01/01/70 00:00 | |
| Ultrasonic Ranging | 01/01/70 00:00 | |
| Matched filter on the rescue | 01/01/70 00:00 | |
| matched filters | 01/01/70 00:00 | |
| Phase locked amplifier | 01/01/70 00:00 | |
| Its a different thing | 01/01/70 00:00 | |
| Ah | 01/01/70 00:00 | |
| Thats the one.... | 01/01/70 00:00 | |
| Clever woman | 01/01/70 00:00 | |
| Just an idea | 01/01/70 00:00 | |
| The scope plot tells it all! | 01/01/70 00:00 | |
| Largest signal | 01/01/70 00:00 | |
| 'Greatest' echo is the wrong criterion! | 01/01/70 00:00 | |
| | 01/01/70 00:00 | |
| somehow I remember... | 01/01/70 00:00 | |
| No, no... | 01/01/70 00:00 | |
| Oops~ forgot... | 01/01/70 00:00 | |
| the product | 01/01/70 00:00 | |
| Power of transmission pulse | 01/01/70 00:00 | |
| Preamp circuit Here | 01/01/70 00:00 | |
| Add caps to remove base line noise | 01/01/70 00:00 | |
| Another potential problem... | 01/01/70 00:00 | |
| Problem with ADC? | 01/01/70 00:00 | |
| possible solution to the ADC problem | 01/01/70 00:00 | |
| Ok~ | 01/01/70 00:00 | |
| Debug Result | 01/01/70 00:00 | |
| ADC Sampling and code debugging | 01/01/70 00:00 | |
| sampling time | 01/01/70 00:00 | |
| Adc for Ultrasonic? | 01/01/70 00:00 | |
| Next, comes to "average" | 01/01/70 00:00 | |
| Why use the adc? | 01/01/70 00:00 | |
| Forgot to tell... | 01/01/70 00:00 | |
| Circle in RED | 01/01/70 00:00 | |
| Asking for help again - Filter | 01/01/70 00:00 | |
| Notch | 01/01/70 00:00 | |
| I don't know | 01/01/70 00:00 | |
| DSP | 01/01/70 00:00 | |
| Nah | 01/01/70 00:00 | |
| for the sake of learning | 01/01/70 00:00 | |
| so | 01/01/70 00:00 | |
| I agree | 01/01/70 00:00 | |
| Amplitude | 01/01/70 00:00 | |
| Op amps | 01/01/70 00:00 | |
| 100pF | 01/01/70 00:00 | |
| bypass ?? | 01/01/70 00:00 | |
| Yes | 01/01/70 00:00 | |
| No sort of bypass | 01/01/70 00:00 | |
| BTE054 BTE054USS2 | 01/01/70 00:00 | |
| Better noise control | 01/01/70 00:00 | |
| re: BTE054 | 01/01/70 00:00 | |
| Replace LMV6032 with LM324 | 01/01/70 00:00 | |
| re:low sensitivity | 01/01/70 00:00 | |
| re:no filtering | 01/01/70 00:00 | |
| Note | 01/01/70 00:00 | |
| Notch filter? | 01/01/70 00:00 | |
| No, | 01/01/70 00:00 | |
| Bandpass | 01/01/70 00:00 | |
| NOT a criticism | 01/01/70 00:00 | |
| Update... | 01/01/70 00:00 | |
| Umm... Nowadays? | 01/01/70 00:00 | |
| Op amp parameters | 01/01/70 00:00 | |
| "Filters for Dummy" | 01/01/70 00:00 | |
| Have you tried it with ..... | 01/01/70 00:00 | |
| Yes, I've tried it and it works well | 01/01/70 00:00 | |
| Basic electronics | 01/01/70 00:00 | |
| 0.002uF -> 3300uF | 01/01/70 00:00 | |
| re:noise | 01/01/70 00:00 | |
| Exactly the same | 01/01/70 00:00 | |
| test of signal | 01/01/70 00:00 | |
| It's over 1.2m | 01/01/70 00:00 | |
| TWO bypass caps. | 01/01/70 00:00 | |
| Two were found | 01/01/70 00:00 | |
| Usenet | 01/01/70 00:00 | |
| Why using a PLL, when a bandpass can ... | 01/01/70 00:00 | |
| which is why ,,,, | 01/01/70 00:00 | |
| Not sure what you meant.. | 01/01/70 00:00 | |
| Already | 01/01/70 00:00 | |
| But it MUST work properly!! | 01/01/70 00:00 | |
| Circuit here | 01/01/70 00:00 | |
| Op-amp to replace LM324 | 01/01/70 00:00 | |
| Non-inverting Input Voltage Divider | 01/01/70 00:00 | |
| LM567 | 01/01/70 00:00 | |
| re:LM324 | 01/01/70 00:00 | |
| re:wrong link | 01/01/70 00:00 | |
| No AGC | 01/01/70 00:00 | |
| AGC | 01/01/70 00:00 | |
| Yes | 01/01/70 00:00 | |
| re: no AGC | 01/01/70 00:00 | |
| LMC6032 is much more linear than LM324 | 01/01/70 00:00 | |
| re: | 01/01/70 00:00 | |
| re:attenuation of signal | 01/01/70 00:00 | |
| Good ones and bad ones | 01/01/70 00:00 | |
| another article of interest | 01/01/70 00:00 | |
| tramsmit & receive | 01/01/70 00:00 | |
| how to measure the distance perfectly? | 01/01/70 00:00 | |
| Fatal Error! | 01/01/70 00:00 | |
| How about this one.... | 01/01/70 00:00 | |
| Ultrasonic Detection Code! | 01/01/70 00:00 | |
| is that right? | 01/01/70 00:00 | |
| Not right,,,,, | 01/01/70 00:00 | |
| Thanks! | 01/01/70 00:00 | |
| another missing! | 01/01/70 00:00 | |
| i'll try it.. | 01/01/70 00:00 | |
| Some Applications of ultrasonic | 01/01/70 00:00 | |
| "Op amps for everyone" | 01/01/70 00:00 | |
| woo... tiring trip | 01/01/70 00:00 | |
| Check this one | 01/01/70 00:00 | |
| Thanks | 01/01/70 00:00 | |
| is it not fundamentally wrong | 01/01/70 00:00 | |
| Both | 01/01/70 00:00 | |
| I knew that... | 01/01/70 00:00 | |
| Synthetic grounds | 01/01/70 00:00 | |
| no, Kai | 01/01/70 00:00 | |
| Steve, Erik | 01/01/70 00:00 | |
| The circuit works, but... | 01/01/70 00:00 | |
| Moral | 01/01/70 00:00 | |
| Puh, what antennas... | 01/01/70 00:00 | |
| Which means I can't use breadboard | 01/01/70 00:00 | |
| In one word. | 01/01/70 00:00 | |
| Using the LM318 | 01/01/70 00:00 | |
| Missing 10K | 01/01/70 00:00 | |
| More caps | 01/01/70 00:00 | |
| Where? | 01/01/70 00:00 | |
| Parallel | 01/01/70 00:00 | |
| Does it work now? | 01/01/70 00:00 | |
| Yes, it works fine | 01/01/70 00:00 | |
| Theoretical work missed | 01/01/70 00:00 | |
| Fatal Error! | 01/01/70 00:00 | |
| Another article to peruse | 01/01/70 00:00 | |
| Another one... | 01/01/70 00:00 | |
| same application | 01/01/70 00:00 | |
| Sorry | 01/01/70 00:00 | |
| Why sorry? | 01/01/70 00:00 | |
| That's exactly what I want to do | 01/01/70 00:00 | |
| which one is the best way? | 01/01/70 00:00 | |
| Capacitors | 01/01/70 00:00 | |
| i've got it | 01/01/70 00:00 | |
| not the best solution | 01/01/70 00:00 | |
| Laser ranging | 01/01/70 00:00 | |
| how much | 01/01/70 00:00 | |
| I've withdrawn from the competition | 01/01/70 00:00 | |
| NOT finance | 01/01/70 00:00 | |
| Re: money is not everything | 01/01/70 00:00 | |
| Good Luck | 01/01/70 00:00 | |
| good luck | 01/01/70 00:00 | |
| Good luck | 01/01/70 00:00 | |
| Thanks! | 01/01/70 00:00 | |
| The noise again | 01/01/70 00:00 | |
| re:link | 01/01/70 00:00 | |
| Link | 01/01/70 00:00 | |
| this is the link | 01/01/70 00:00 | |
| re:noise | 01/01/70 00:00 | |
| 5-14 Khz | 01/01/70 00:00 | |
| re:5-14kHz | 01/01/70 00:00 | |
| The Noise Amplitude | 01/01/70 00:00 | |
| gain | 01/01/70 00:00 | |
| the problem is gain | 01/01/70 00:00 | |
| Schematic | 01/01/70 00:00 | |
| Thank You but... | 01/01/70 00:00 | |
| Thank You but... | 01/01/70 00:00 | |
| 1/4Watt is enough | 01/01/70 00:00 | |
| Simulation result | 01/01/70 00:00 | |
| Strange plots... | 01/01/70 00:00 | |
| How about Compensation? | 01/01/70 00:00 | |
| Not needed | 01/01/70 00:00 | |
| Bigger Pulse | 01/01/70 00:00 | |
| Bridge configuration can help | 01/01/70 00:00 | |
| The same circuit but... | 01/01/70 00:00 | |
| ...but much stronger | 01/01/70 00:00 | |
| I have tried | 01/01/70 00:00 | |
| What do you mean by ripple? | 01/01/70 00:00 | |
| The ripple | 01/01/70 00:00 | |
| No, it is not. The output from a logic | 01/01/70 00:00 | |
| Answer | 01/01/70 00:00 | |
| Yup Kai | 01/01/70 00:00 | |
| It's to adjust oscillating frequency | 01/01/70 00:00 | |
Finished | 01/01/70 00:00 | |
| Exams VS academic | 01/01/70 00:00 | |
| "Plan B" | 01/01/70 00:00 | |
| Universities in HongKong | 01/01/70 00:00 |