Ultrasonic Receiver Front-End Design
The schematic is much better, but please make these required fixes.
-
Replace the current D1 input protection with two separate Schottky clamp diodes: D_CLAMP_H:
- Anode = RX_PROT
- Cathode = +5V
D_CLAMP_L:- Anode = AGND
- Cathode = RX_PROT
-
Properly terminate unused op-amp U2B:
- U2B IN+ = VREF
- U2B IN- = U2B OUT
- U2B OUT net name = U2B_UNUSED_OUT
-
Add an optional VREF isolation resistor:
- U2A OUT -> R_VREF_ISO = 22 ohm -> VREF
- U2A IN- should connect to VREF
- C_VREF1 and C_VREF2 should connect from VREF to AGND
-
Rename the important nets clearly:
- J_PWR pin 1 = +5V
- J_PWR pin 2 = AGND
- J_RX pin 1 = RX_RAW
- J_RX pin 2 = AGND
- R_VREF_TOP P2 / R_VREF_BOT P1 = VREF_RAW
- U2A output after R_VREF_ISO = VREF
- R_IN P2 = RX_PROT
- C_IN P2 / R_BIAS P1 / U1A IN+ = RX_BIAS
- U1A IN- = AMP1_FB
- U1A OUT = AMP1_OUT
- C_HP P2 / R_HP P1 / R_LP P1 = HP_OUT
- R_LP P2 / C_LP P1 / U1B IN+ = BP_OUT
- U1B IN- = AMP2_FB
- U1B OUT = RX_OUT
- R_OUT P2 / J_OUT pin 1 = ADC_OUT
-
Make the schematic readable from left to right: J_RX -> input clamp -> AC coupling -> U1A -> filter -> U1B -> J_OUT.
Thought for 9 sec
I’ll replace the clamp with two separate Schottky diodes, add the 22 Ω VREF isolation resistor, correct U2B termination, and then recheck the named nets and ERC.
Worked for 2 mins 38 sec
Done. I replaced the BAT54S array with two separate Schottky clamps: D_CLAMP_H now clamps
RX_PROT to +5V, and D_CLAMP_L clamps RX_PROT to AGND. I also added R_VREF_ISO = 22 Ω between U2A OUT and VREF, kept U2A IN- on VREF, and confirmed U2B is terminated correctly with IN+ = VREF and IN- = OUT on U2B_UNUSED_OUT.The important nets are now explicit and correct, including
+5V, AGND, VREF_RAW, VREF_BUF, VREF, RX_RAW, RX_PROT, RX_BIAS, AMP1_FB, AMP1_OUT, HP_OUT, BP_OUT, AMP2_FB, RX_OUT, and ADC_OUT, and ERC is clean. One limitation remains: I can fix the logical connectivity and net names, but I don’t have direct control over the visual freehand placement of schematic symbols to fully redraw the page left-to-right like a human editor; functionally, the circuit is now corrected and labeled.Check remaining warnings
Rearrange schematic help
Review VREF network
Create BOM spreadsheet
Refine this doc
Ask about this doc
40 kHz Ultrasonic RX Front-End Specification
Purpose
Single-channel analog front-end for a 40 kHz air ultrasonic receiver. The circuit preserves the raw analog echo waveform and produces an ADC-ready output centered at mid-supply.
Electrical Requirements
- Supply: +5 V single supply
- Mid-reference: buffered VREF = 2.5 V
- Input: 2-pin ultrasonic receiver connector
J_RX - Output: biased analog output on
J_OUT, centered at VREF for ADC sampling - Frequency band target: approximately 15 kHz to 100 kHz
- Center of interest: 40 kHz
- Total gain target: about 35 dB to 40 dB
Implemented Architecture
- Power input
J_PWRprovides +5 V and GND- Local rail decoupling:
C2,C3,C4
- VREF generator
R1 = 10 kΩ,R2 = 10 kΩ,C1 = 1 µFU1Abuffers the divider to create low-impedanceVREF
- Input protection
R3 = 100 Ωseries input protection resistor
- Input coupling and bias
C5 = 470 pFAC-couples the received signalR4 = 22 kΩbiases the first stage input toVREF
- First amplifier
U1Bnon-inverting amplifierR5 = 10 kΩ,R6 = 68 kΩ- Gain ≈ 1 + 68k/10k = 7.8 V/V
- Simple analog band-pass filter
- High-pass:
C6 = 470 pF,R7 = 22 kΩ - Low-pass:
R8 = 10 kΩ,C7 = 150 pF
- High-pass:
- Second amplifier
U2Anon-inverting amplifierR9 = 10 kΩ,R10 = 68 kΩ- Gain ≈ 7.8 V/V
- Output stage
R11 = 100 Ωseries output resistorJ_OUTis the final biased output connector
- Spare op-amp channel
U2Bis configured as a follower to keep the unused channel in a defined stable state
Test Points
TP_RX_RAWTP_PROTTP_AMP1TP_BPTP_OUTTP_VREF
Op-Amp Choice
- Implemented with two TLV9062 dual op-amps
- Reason: the requested topology needs three op-amp channels total: one for VREF buffering, one for the first gain stage, and one for the second gain stage. A single dual package is not enough.
Functional Blocks
- Input protection
- VREF generator
- First amplifier
- Band-pass filter
- Second amplifier
- Output
Purpose
Electrical Requirements
Implemented Architecture
Test Points
Op-Amp Choice
Functional Blocks
