Frequent contributor Nick Cornford lately assembled an ensemble of cool circuit designs incorporating linear-in-pitch VCOs (LPVCOs).
- “A pitch-linear VCO, half 1: Getting it going”
- “A pitch-linear VCO, half 2: taking it additional”
- “Revealing the infrasonic underworld cheaply, Half 1”
- “Revealing the infrasonic underworld cheaply, Half 2”
These elegant and revolutionary designs (commonplace fare for Nick’s contributions) have been completely enough for his or her supposed functions. Nonetheless, it received me questioning how tough it could be to implement an LPVCO with a spread protecting the complete 10-octave audio spectrum, from 20 Hz to twenty kHz. I even determined to strive for further credit score by going for a tri-wave output appropriate for direct drive of certainly one of Nick’s well-known squish-diode sine converters. Determine 1 exhibits the consequence.
Determine 1 An LPVCO with 10-octave (20 Hz to twenty kHz) tri-wave output contains antilog pair Q1 and Q2, two-way present mirror Q3 and This fall, integrator A1b, comparator A1a, and buffer A1c. Resistors R1 and R2 are precision varieties, and T1 is a Vishay NTCSC0201E3103FLHT (inhale!).
Wow the engineering world together with your distinctive design: Design Concepts Submission Information
Vin is scaled by the tempco-compensating voltage divider, ((R1+T1)/R2 + 1) = 28:1, and utilized to the Q1 and Q2 antilog pair, the place Q1 degree shifts and additional temperature compensates it. Then, with the assistance of buffer A1c, it’s antilogged and inverted by Q2 to supply Ic2 = 2(2Vin) µA = 1 µA to 1 mA for Vin = 0 to 5v.
From there, it goes to the two-way present mirror: Q3 and This fall. An outline of how the TWCM works could be discovered right here in “A two-way mirror—present mirror that’s.”
The TWCM passes Ic2 by way of to the integrator A1b if comparator A1a’s output is zero, and mirrors (inverts) it if A1a’s output is excessive. Thus, A1b ramps up if A1a’s output is at 0v, and down if it’s at 5v, leading to sustained oscillation.
The C1 timing ramp has a period in every route starting from 25 ms (for Vin = 0) to 25 µs (for Vin = 5v). The triangular cycle will due to this fact repeat at Fosc = 2(2Vin)µA/(25nCb)/2 = 20(2(2Vin) ) Hz.
So, there’s the aim of a tri-wave LPVCO with an output span of 20 Hz to twenty kHz centered at 640 Hz, and it wasn’t so terribly messy to get there in spite of everything!
My thanks go to Nick Cornford for introducing the LPVCO to Design Concepts (DIs), and to Christopher Paul and Andy I for his or her extremely useful simulations and constructive criticisms of my halting steps to temperature-compensating antilogging circuits. I additionally thank editor Aalyia Shaukat for her DI surroundings that makes such teamwork potential for a gang of opinionated engineers, and largely completed with out precise bloodshed!
Principally.
Stephen Woodward’s relationship with EDN’s DI column goes again fairly a great distance. Over 100 submissions have been accepted since his first contribution again in 1974.
Associated Content material
- Seven-octave linear-in-pitch VCO
- A pitch-linear VCO, half 1: Getting it going
- A pitch-linear VCO, half 2: taking it additional
- Revealing the infrasonic underworld cheaply, Half 1
- Revealing the infrasonic underworld cheaply, Half 2
The submit 10-octave linear-in-pitch VCO with buffered tri-wave output appeared first on EDN.
