Blackmer’s VCA Cell Implemented Using Subthreshold MOSFETs

Lanterman AD, Hasler JO. Blackmer’s VCA Cell Implemented Using Subthreshold MOSFETs. J Audio Eng Soc. 2024;72(11):813-824. doi:10.17743/jaes.2022.0170

@article{Lanterman2024_22781,
  author = {Lanterman, Aaron D. and Hasler, Jennifer O.},
  title = {{Blackmer’s VCA Cell Implemented Using Subthreshold MOSFETs}},
  journal = {Journal of the Audio Engineering Society},
  volume = {72},
  number = {11},
  pages = {813--824},
  year = {2024},
  month = nov,
  publisher = {Audio Engineering Society},
  doi = {10.17743/jaes.2022.0170},
  url = {https://doi.org/10.17743/jaes.2022.0170}
}

TY  - JOUR
TI  - Blackmer’s VCA Cell Implemented Using Subthreshold MOSFETs
AU  - Lanterman, Aaron D.
AU  - Hasler, Jennifer O.
T2  - Journal of the Audio Engineering Society
J2  - J. Audio Eng. Soc.
VL  - 72
IS  - 11
SP  - 813
EP  - 824
PY  - 2024
DA  - 2024/11/13
DO  - 10.17743/jaes.2022.0170
UR  - https://doi.org/10.17743/jaes.2022.0170
PB  - Audio Engineering Society
LA  - en
AB  - In 1973, David Blackmer introduced a voltage-controlled amplifier consisting of a pair of negative-positive-negative transistors performing logging and antilogging functions coupled with a complementary positive-negative-positive pair. This “Blackmer cell” has been widely used in studio equipment such as compressors and mixers. The authors consider replacing the bipolar junction transistors with metal-oxide-semiconductor field-effect transistors in the subthreshold region to exploit the resulting exponential voltage/current relationship, particularly focusing on its implementation on a field-programmable analog array. Resistors used for input voltage-to-current conversion and output current-to-voltage current conversion are replaced with operational transconductance amplifiers. Simulations show that the circuit may be expected to work well as a voltage-controlled attenuator but may react catastrophically when attempting gains greater than unity due to the nonlinearity of the output operational transconductance amplifier. The effect of various mismatches in transistor parameters is studied.
ER  -