Operational amplifiers for tone control circuit application require high slew rate, wide bandwidth, high input impedance, and high output current characteristics, and CA3140 is suitable for this purpose. Look at the following tone control circuit’s schematic diagram for the design.
The tone control circuit in the figure above use a very popular Baxandall tone control configuration circuit, which has unity gain (gain=1) at midband and uses standard linear potentiometers. Low cost, low value, and small size capacitors is possible to implement because of the very high input impedance of CA3140. A ±15dB bass-treble boost and cut are set at frequency point of 100Hz and 10kHz. Because of excellent high slew rate characteristic of this op-amp, full peak-to-peak output is available event at 20KHz. The amplifier gain is decreased -3dB from flat response at 70KHz, and it’s beyond audible frequency range to make sure this tone control circuit handle the audio range perfectly. [Circuit’s schematic diagram source: Intersil’s CA3140 Application Notes]