# 555 Calc vs Operational Amplifiers Guide

The clearest difference is update cadence: Operational Amplifiers Guide at every 2 months against 555 Calc's every 20 months. 555 Calc's advantage is iOS requirement (11.0 vs 16.0). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

555 Calc ships an update every 20 months, Operational Amplifiers Guide every 2 months. The most recent releases landed on September 27, 2026 and September 19, 2026 respectively.

## The numbers

| Metric | 555 Calc | Operational Amplifiers Guide |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.0 (3 ratings)](https://appshunter.io/ios/app/555-calc/id868058244/reviews)** | — |
| Number of ratings | **3** | — |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | No | No |
| Ads | Yes | Yes |
| Update frequency | Every 20 months | **Every 2 months** |
| Monetization | Ad-supported | — |
| Size | 18 MB | 17 MB |
| Requires iOS | **11.0** | 16.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Jibiki Works](https://appshunter.io/developer/556845808) | [ALG Software Lab](https://appshunter.io/developer/1650561236) |

## What reviewers say

### 555 Calc

[App page](https://appshunter.io/ios/app/555-calc/id868058244)

This utility app helps engineers and hobbyists calculate resistor values for circuits using the Timer IC 555. Simply input frequency, duty ratio, and capacitor values to get the required resistor outputs.

**Highlights:** Calculate resistor values, Input frequency, Input duty ratio, Input capacitor value, Timer IC 555 circuit design

**Features:** macOS Compatibility

**In-app purchases:** none


### Operational Amplifiers Guide

[App page](https://appshunter.io/ios/app/operational-amplifiers-guide/id6467499897)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is 555 Calc free?

555 Calc is free to download, with no in-app purchases.

### Is Operational Amplifiers Guide free?

Operational Amplifiers Guide is free to download, with no in-app purchases.

### Do 555 Calc or Operational Amplifiers Guide have ads?

Both 555 Calc and Operational Amplifiers Guide show ads.

### Which is updated more often, 555 Calc or Operational Amplifiers Guide?

555 Calc ships an update every 20 months, and Operational Amplifiers Guide every 2 months. Most recently, 555 Calc was updated on September 27, 2026 and Operational Amplifiers Guide on September 19, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*