SBOA229 June 2021 OPA325 , TLV316 , TLV9062

Input | Output | Supply | |||
---|---|---|---|---|---|

V_{iMin} | V_{iMax} | V_{oMin} | V_{oMax} | V_{cc} | V_{ee} |

–2.45V | +2.45V | 0.05V | 4.95V | 5V | 0V |

Gain | Low Cutoff Frequency (f_{l}) | High Cutoff Frequency (f_{h}) | V_{ref} |
---|---|---|---|

1V/V | 1kHz | 10kHz | 2.5V |

**Design Description**

This circuit is a single-supply, 2nd-order Sallen-Key (SK) band-pass (BP) filter. It is designed by cascading an SK low-pass filter and an SK high-pass filter. Vref provides a DC offset to accommodate for a single supply.

**Design Notes**

- Select an op amp with sufficient input common-mode range and output voltage swing.
- Add V
_{ref}to bias the input signal to meet the input common-mode range and output voltage swing. - Select the capacitor values first since standard capacitor values are more coarsely subdivided than the resistor values. Use high-precision, low-drift capacitor values to avoid errors in f
_{l}and f_{h}. - To minimize the amount of slew-induced distortion, select an op amp with sufficient slew rate (SR).
- For HP filters, the maximum frequency is set by the gain bandwidth (GBW) of the op amp. Therefore, be sure to select an op amp with sufficient GBW.

**Design Steps**

This BP filter design involves two cascaded filters, a low-pass (LP) filter and a high-pass (HP) filter. The lower cutoff frequency (f_{l}) of the BP filter is 1kHz and the higher cutoff frequency (f_{h}) is 10kHz. The design steps show an LP filter design with f_{h} of 10kHz and an HP filter design with f_{l} of 1kHz. See the SK LP filter design and SK HP filter design in the circuit cookbook for details on transfer function equations and calculations.

**LP Filter Design**

- Use SK low-pass filter design to determine R
_{1}and R_{2}.${\text{R}}_{1}\text{= 10k\Omega ,}\phantom{\rule{0ex}{0ex}}{\text{R}}_{2}\text{= 10k\Omega}$ - Use SK low-pass filter design to determine C
_{1}and C_{2}.${\text{C}}_{1}\text{= 2.2nF}(\text{StandardValue}),\phantom{\rule{0ex}{0ex}}{\text{C}}_{2}\text{= 1.1nF}(\text{StandardValue})$

**HP Filter Design**

- Use SK high-pass filter design to determine C
_{3}and C_{4}.${\text{C}}_{\text{3}}\text{= 10nF,}\phantom{\rule{0ex}{0ex}}{\text{C}}_{4}\text{= 10nF}$ - Use SK high-pass filter design to determine R
_{3}and R_{4}.${\text{R}}_{3}\text{= 11k\Omega ,}\phantom{\rule{0ex}{0ex}}{\text{R}}_{4}\text{= 23k\Omega}$

**Design Simulations**

**AC Simulation Results**

**Transient Simulation Results**

The following image shows a filter output in response to a 5-V_{pp}, 100-Hz input signal (gain = 0.01 V/V).

The following transient simulation result shows a filter output in response to a 5-V_{pp}, 5-kHz input signal

(gain = 1V/V).

The following image shows a filter output in response to a 5-V_{pp}, 100-kHz input signal (gain = 0.01V/V).

**Design References**

- See Analog Engineer's Circuit Cookbooks for TI's comprehensive circuit library.
- TI Precision Labs.

**Design Featured Op Amp**

TLV9062 | |
---|---|

Vss | 1.8V to 5.5V |

V _{inCM}_{} | Rail-to-Rail |

Vout | Rail-to-Rail |

Vos | 0.3mV |

Iq | 538µA |

Ib | 0.5pA |

UGBW | 10MHz |

SR | 6.5V/µs |

#Channels | 1, 2, 4 |

www.ti.com/product/TLV9062 |

**Design Alternate Op Amp**

TLV316 | OPA325 | |
---|---|---|

V_{ss} | 1.8V to 5.5V | 2.2V to 5.5V |

V_{inCM} | Rail-to-Rail | Rail-to-Rail |

Vout | Rail-to-Rail | Rail-to-Rail |

V_{os} | 0.75mV | 0.150mV |

Iq | 400µA | 650µA |

Ib | 10pA | 0.2pA |

UGBW | 10MHz | 10MHz |

SR | 6V/µs | 5V/µs |

#Channels | 1, 2, 4 | 1, 2, 4 |

www.ti.com/product/TLV316 | www.ti.com/product/OPA325 |