# Timer 555 Calculator Pro vs Operational Amplifiers Pro

The clearest difference is rating: Operational Amplifiers Pro at 5.0 against Timer 555 Calculator Pro's 4.7. Timer 555 Calculator Pro's advantage is price ($0.99 vs $4.99) and ratings volume (3 vs 1). On update cadence, ads, in-app purchases and monetization model there is nothing between them.

Timer 555 Calculator Pro costs $0.99 and Operational Amplifiers Pro $4.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Operational Amplifiers Pro holds the better App Store score, 5.0 against 4.7. Both are backed by a comparable volume of ratings — 3 and 1 respectively.

Timer 555 Calculator Pro ships an update every 3 months, Operational Amplifiers Pro every 2 months. The most recent releases landed on June 4, 2026 and September 25, 2026 respectively.

## The numbers

| Metric | Timer 555 Calculator Pro | Operational Amplifiers Pro |
| --- | --- | --- |
| Price | **$0.99** | $4.99 |
| Rating | [4.7 (3 ratings)](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125/reviews) | **[5.0 (1 ratings)](https://appshunter.io/ios/app/operational-amplifiers-pro/id6467253953/reviews)** |
| Number of ratings | **3** | 1 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 3 months | **Every 2 months** |
| Monetization | Paid | Paid |
| Size | 3 MB | 14 MB |
| Requires iOS | **13.2** | 16.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Mac |
| Age rating | 4+ | 4+ |
| Developer | [Siu Yuen Ho](https://appshunter.io/developer/814088527) | [ALG Software Lab](https://appshunter.io/developer/1650561236) |

## What reviewers say

### Timer 555 Calculator Pro

[App page](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125)

Calculate parameters for monostable and astable circuits. Find component combinations for desired pulse width or frequency. Share circuit files via iCloud Drive or AirDrop.

**Highlights:** Calculate monostable pulse width, Calculate astable frequency, Find component combinations, Adjust component tolerance, Unlimited combinations (Pro), Share circuit files

**In-app purchases:** none


### Operational Amplifiers Pro

[App page](https://appshunter.io/ios/app/operational-amplifiers-pro/id6467253953)

This app provides interactive calculators and reference information for designing and analyzing op-amp circuits. It offers step-by-step explanations and technical data on popular op-amp series, aiding students and engineers in circuit development and prototyping.

**Highlights:** Interactive op-amp circuit calculators, Step-by-step explanations and formulas, Reference data on op-amps and comparators, Support for 14 languages, Light and dark mode, Advanced calculators and circuit guides (Pro), Full-text search (Pro)

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Timer 555 Calculator Pro free?

Timer 555 Calculator Pro costs $0.99, with no in-app purchases.

### Is Operational Amplifiers Pro free?

Operational Amplifiers Pro costs $4.99, with no in-app purchases.

### Which has better reviews, Timer 555 Calculator Pro or Operational Amplifiers Pro?

Operational Amplifiers Pro is rated higher. Timer 555 Calculator Pro averages 4.7 out of 5 from 3 ratings, while Operational Amplifiers Pro averages 5.0 from 1 ratings.

### Do Timer 555 Calculator Pro or Operational Amplifiers Pro have ads?

Neither Timer 555 Calculator Pro nor Operational Amplifiers Pro shows ads.

### Which is updated more often, Timer 555 Calculator Pro or Operational Amplifiers Pro?

Timer 555 Calculator Pro ships an update every 3 months, and Operational Amplifiers Pro every 2 months. Most recently, Timer 555 Calculator Pro was updated on June 4, 2026 and Operational Amplifiers Pro on September 25, 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.*